Ink and ink set for ink jet printing and method of ink jet printing

ABSTRACT

An inkjet recording ink composition comprising an aqueous medium having dissolved and/or dispersed therein at least one dye, wherein at least one betaine-type surfactant is contained in the ink composition. The dye used is preferably a magenta dye having a specific azo structure or a cyanine dye having a specific phthalocyanine structure. By virtue of such a constitution, an inkjet recording ink composition excellent in ejection property, light fastness, heat fastness and oxidation resistance and causing less dye bleeding can be provided.

TECHNICAL FIELD

The present invention relates to an inkjet recording ink compositionensuring excellent image stability under high-humidity condition, and aninkjet recording method using the ink composition.

BACKGROUND ART

Accompanying recent popularization of computers, an inkjet printer iswidely used for printing letters or an image on paper, film, cloth orthe like not only at offices but also at homes.

The inkjet recording method includes a system of jetting out a liquiddroplet by applying a pressure from a piezoelectric element, a system ofjetting out a liquid droplet by generating a bubble in the ink underheat, a system of using an ultrasonic wave, and a system of jetting outa liquid droplet by suction using an electrostatic force. The inkcomposition used for such inkjet recording includes an aqueous ink, anoily ink and a solid (fusion-type) ink. Among these inks, an aqueous inkis predominating in view of production, handleability, odor, safety andthe like.

The coloring agent used in such an inkjet recording ink is required tohave high solubility in a solvent, enable high-density recording,provide good color hue, exhibit excellent fastness to light, heat, air,water and chemicals, ensure good fixing to an image-receiving materialand less bleeding, give an ink having excellent storability, have highpurity and no toxicity, and be available at a low cost. However, it isvery difficult to find out a coloring agent satisfying theserequirements in a high level. Various dyes and pigments for inkjetrecording have been already proposed and are actually used, but acoloring agent satisfying all of the requirements is not yet found outat present. Conventionally well-known dyes and pigments having a colorindex (C.I.) number can hardly satisfy both color hue and fastnessrequired of the inkjet recording ink. Heretofore, studies are being madeon a dye having fastness and good color hue with an attempt to develop adye excellent as the dye for inkjet recording.

However, in the compound as a water-soluble dye, a water-soluble groupis necessarily substituted. If the number of water-soluble groups isincreased so as to improve the stability of ink, this has been found tocause a problem that the formed image is readily blurred underhigh-humidity conditions.

An object of the present invention is to provide an inkjet recording inkcomposition and an inkjet recording method, which cause less blurring ofimage under high-humidity conditions.

DISCLOSURE OF THE INVENTION

The object of the present invention can be attained by the followingtechniques.

1. An inkjet recording ink composition comprising an aqueous mediumhaving dissolved and/or dispersed therein at least one dye, wherein atleast one betaine-type surfactant is contained in the ink composition.

2. The inkjet recording ink composition as described in 1, wherein inthe molecule of the betaine-type surfactant, the cationic moiety is aquaternary nitrogen atom and the anionic moiety is a carboxyl group or asulfo group.

3. The inkjet recording ink composition as described in 1 or 2, whereinthe betaine-type surfactant is a compound with the N-position ofimidazole being substituted by a carboxyalkyl group (compound A), or analkylamine salt compound having an alkyl substituted by a carboxyl groupor a sulfo group (compound B).

4. The inkjet recording ink composition as described in 3, wherein thecompound A is a compound represented by formula (A):

wherein R_(s1) and R_(s2) each represents an alkyl group, and R_(s3)represents a carboxyl or sulfo group-containing alkyl group.

5. The inkjet recording ink composition as described in 3, wherein thecompound B is a compound represented by formula (B):

wherein R_(s4), R_(s5) and R_(s6) each independently represents an alkylgroup, an aryl group or a heterocyclic group and may combine with eachother to form a ring structure, and R_(s7) represents a carboxyl orsulfo group-containing alkyl group.

6. The inkjet recording ink composition as described in 5, wherein inthe compound represented by formula (B), R_(s4), R_(s5) and R_(s6) eachindependently represents an alkyl group and the carboxyl grouprepresented by R_(s7) is represented by -L-COO⁻ (wherein L represents alinking group).

7. The inkjet recording ink composition as described in 6, wherein inthe compound represented by formula (B), L represents CH(R_(s8)), R_(s8)represents a hydrogen atom or an alkyl group having 8 or more carbonatoms, and at least one of R_(s4), R_(s5), R_(s6) and R_(s8) is an alkylgroup having 8 or more carbon atoms.

8. The inkjet recording ink composition as described in any one of 1 to7, wherein the dye is an azo dye having an absorption maximum in thespectral region of 500 to 580 nm in the aqueous medium and having anoxidation potential nobler than 1.0 V (vs SCE).

9. The inkjet recording ink composition as described in any one of 1 to8, wherein the azo dye has a chromophore represented by the formula:(heterocyclic ring A) —N═N— (heterocyclic ring B), provided that theheterocyclic ring A and the heterocyclic B may have the same structure.

10. The inkjet recording ink composition as described in any one of 1 to9, wherein the azo dye is an azo dye in which an aromaticnitrogen-containing 6-membered heterocyclic ring is bonded as a couplingcomponent directly to at least one side of the azo group.

11. The inkjet recording ink composition as described in any one of 1 to10, wherein the azo dye is an azo dye having an aromatic ring aminogroup- or heterocyclic amino group-containing structure as anauxochrome.

12. The inkjet recording ink as described in any one of 1 to 11, whereinthe azo dye is an azo dye having a steric structure.

13. The inkjet recording ink composition as described in any one of 1 to12, wherein the azo dye is a dye represented by the following formula(1):

wherein A represents a 5-membered heterocyclic group;

-   -   B¹ and B² each represents ═CR¹≧ or —CR²═ or either one of B¹ and        B² represents a nitrogen atom and the other represents ═CR¹— or        —CR²═;    -   R⁵ and R⁶ each independently represents a hydrogen atom or a        substituent, the substituent is an aliphatic group, an aromatic        group, a heterocyclic group, an acyl group, an alkoxycarbonyl        group, an aryloxycarbonyl group, a carbamoyl group, an        alkylsulfonyl group, an arylsulfonyl group or a sulfamoyl group,        and the hydrogen atom of each substituent may be substituted;    -   G, R¹ and R² each independently represents a hydrogen atom or a        substituent, the substituent is a halogen atom, an aliphatic        group, an aromatic group, a heterocyclic group, a cyano group, a        carboxyl group, a carbamoyl group, an alkoxycarbonyl group, an        aryloxycarbonyl group, a heterocyclic oxycarbonyl group, an acyl        group, a hydroxy group, an alkoxy group, an aryloxy group, a        heterocyclic oxy group, a silyloxy group, an acyloxy group, a        carbamoyloxy group, an alkoxycarbonyloxy group, an        aryloxycarbonyloxy group, an amino group, an acylamino group, a        ureido group, a sulfamoylamino group, an alkoxycarbonylamino        group, an aryloxycarbonylamino group, an alkylsulfonylamino        group, an arylsulfonylamino group, a heterocyclic sulfonylamino        group, a nitro group, an alkylthio group, an arylthio group, a        heterocyclic thio group, an alkylsulfonyl group, an arylsulfonyl        group, a heterocyclic sulfonyl group, an alkylsulfinyl group, an        arylsulfinyl group, a heterocyclic sulfinyl group, a sulfamoyl        group or a sulfo group, and the hydrogen atom of each        substituent may be substituted; and    -   R¹ and R⁵, or R⁵ and R⁶ may combine to form a 5- or 6-membered        ring.

14. The inkjet recording ink composition as described in any one of 1 to13, wherein the ozone discoloration rate constant of recorded image is5.0×10⁻² [hour⁻¹] or less.

15. The inkjet recording ink composition as described in any one of 1 to7, wherein the dye is a water-soluble phthalocyanine dye having anoxidation potential nobler than 1.0 V.

16. The inkjet recording ink composition as described in any one of 1 to7 and 15, wherein after storage in an ozone environment of 5 ppm for 24hours, the monochromatic moiety printed by using a single (cyan) colorof the ink to give a cyan reflection density of 0.9 to 1.1 in a Status Afilter has a coloring matter residual ratio (density afterdiscoloration/initial density×100) of 60% (preferably 80%) or more.

17. The inkjet recording ink composition as described in any one of 1 to7, 15 and 16, wherein after discoloration with ozone under theconditions of 16, the amount of Cu ion flowed out from the ink intowater is 20% or less of all dyes.

18. The inkjet recording ink composition as described in any one of 1 to7 and 15 to 17, wherein the phthalocyanine dye is a water-soluble dyehaving an electron-withdrawing group at the β-position of a benzene ringof the phthalocyanine.

19. The inkjet recording ink composition as described in any one of 1 to7 and 15 to 18, wherein the phthalocyanine dye is a water-solublephthalocyanine dye produced by a process not passing through sulfonationof an unsubstituted phthalocyanine.

20. The inkjet recording ink composition as described in 1 to 7 and 15to 19, wherein the phthalocyanine dye is represented by the followingformula (I):

wherein X₁, X₂, X₃ and X₄ each independently represents —SO-Z, —SO₂-Z,—SO₂NR1R2, a sulfo group, —CONR1R2 or —CO₂R1;

-   -   Z represents a substituted or unsubstituted alkyl group, a        substituted or unsubstituted cycloalkyl group, a substituted or        unsubstituted alkenyl group, a substituted or unsubstituted        aralkyl group, a substituted or unsubstituted aryl group, or a        substituted or unsubstituted heterocyclic group, and R1 and R2        each independently represents a hydrogen atom, a substituted or        unsubstituted alkyl group, a substituted or unsubstituted        cycloalkyl group, a substituted or unsubstituted alkenyl group,        a substituted or unsubstituted aralkyl group, a substituted or        unsubstituted aryl group, or a substituted or unsubstituted        heterocyclic group, provided that when a plurality of Zs are        present, these may be the same or different;    -   Y₁, Y₂, Y₃ and Y₄ each independently represents a monovalent        substituent;    -   provided that when a plurality of X₁s, X₂s, X₃s, X₄s, Y₁s, Y₂s,        Y₃s or Y₄s are present, these may be the same or different;    -   a₁ to a₄ and b₁ to b₄ represent the number of substituents X₁ to        X₄ and Y₁ to Y₄, respectively, a₁ to a₄ each independently        represents an integer of 0 to 4 but all are not 0 at the same        time, and b₁ to b₄ each independently represents an integer of 0        to 4; and    -   M represents a hydrogen atom, a metal atom or an oxide,        hydroxide or halide thereof.

21. The inkjet recording ink composition as described in 20, wherein thedye represented by formula (I) is a dye represented by the followingformula (II):

wherein X₁₁ to X₁₄, Y₁₁ to Y₁₈ and M₁ have the same meanings as X₁ toX₄, Y₁ to Y₄ and M in formula (I) , respectively, and

-   -   a₁₁ to a₁₄ each independently represents an integer of 1 or 2.

22. The inkjet recording ink composition as described in any one of 1 to21, wherein a nonionic surfactant is contained in the ink composition.

23. The inkjet recording ink composition as described in any one of 1 to22, wherein an organic solvent having a boiling point of 150° C. or moreis contained in the ink composition.

24. An inkjet recording ink set comprising at least one inkjet recordingink composition described in any one of 1 to 23.

25. An inkjet recording method comprising recording an image in aninkjet printer by using the inkjet recording ink composition describedin any one of 1 to 23 or the ink set described in 24.

26. The inkjet recording method as described in 25, comprising ejectingink droplets according to recording signals on an image-receivingmaterial comprising a support having thereon an image-receiving layercontaining a white inorganic pigment particle, thereby recording animage on the image-receiving material, wherein the ink droplet comprisesthe inkjet recording ink composition described in any one of 1 to 23.

BEST MODE FOR CARRYING OUT THE INVENTION

Specific embodiments of the present invention are described in detailbelow.

The azo dye which is used as the magenta dye is described in detailbelow.

The azo dye as the magenta dye preferably has the following properties.

In the magenta ink used for the inkjet recording ink of the presentinvention, a magenta dye selected from azo dyes is dissolved ordispersed in an aqueous medium and this dye is fundamentallycharacterized in that the absorption maximum in the aqueous medium ispresent in the spectral region of 500 to 580 nm and the oxidationpotential is nobler than 1.0 V (vs SCE).

The first preferred structural feature of this azo dye is that the dyehas a chromophore represented by the formula: (heterocyclic ring A)—N═N— (heterocyclic ring B). In this case, the heterocyclic rings A andB may have the same structure. Specifically, the heterocyclic rings Aand B each is a 5- or 6-membered heterocyclic ring selected frompyrazole, imidazole, triazole, oxazole, thiazole, selenazole, pyridone,pyrazine, pyrimidine and pyridine. These are specifically described, forexample, in Japanese Patent Application Nos. 2000-15853 and 2001-15614,JP-A-2002-309116 (the term “JP-A” as used herein means an “unexaminedpublished Japanese patent application”) and Japanese Patent ApplicationNo. 2001-195014.

The second preferred structural feature of the azo dye is that anaromatic nitrogen-containing 6-membered heterocyclic ring is bonded as acoupling component directly to at least one side of the azo group.Specific examples thereof are described in 2001-110457.

The third preferred structural feature is that the auxochrome has anaromatic ring amino group or heterocyclic amino group structure,specifically, an anilino group or a heterylamino group.

The fourth preferred structural feature is that the dye has a stericstructure. This is specifically described in Japanese Patent ApplicationNo. 2002-12015.

Among these preferred structural features of the azo dye, the dye mostpreferred for achieving the objects of the present invention is a dyerepresented by the following formula (1):

wherein A represents a 5-membered heterocyclic group;

-   -   B¹ and B² each represents ═CR¹— or —CR²═ or either one of B¹ and        B² represents a nitrogen atom and the other represents ═CR¹— or        —CR²═;    -   R⁵ and R⁶ each independently represents a hydrogen atom or a        substituent, the substituent is an aliphatic group, an aromatic        group, a heterocyclic group, an acyl group, an alkoxycarbonyl        group, an aryloxycarbonyl group, a carbamoyl group, an        alkylsulfonyl group, an arylsulfonyl group or a sulfamoyl group,        and the hydrogen atom of each substituent may be substituted;    -   G, R¹ and R² each independently represents a hydrogen atom or a        substituent, the substituent is a halogen atom, an aliphatic        group, an aromatic group, a heterocyclic group, a cyano group, a        carboxyl group, a carbamoyl group, an alkoxycarbonyl group, an        aryloxycarbonyl group, a heterocyclic oxycarbonyl group, an acyl        group, a hydroxy group, an alkoxy group, an aryloxy group, a        heterocyclic oxy group, a silyloxy group, an acyloxy group, a        carbamoyloxy group, an alkoxycarbonyloxy group, an        aryloxycarbonyloxy group, an amino group, an acylamino group, a        ureido group, a sulfamoylamino group, an alkoxycarbonylamino        group, an aryloxycarbonylamino group, an alkylsulfonylamino        group, an arylsulfonylamino group, a heterocyclic sulfonylamino        group, a nitro group, an alkylthio group, an arylthio group, a        heterocyclic thio group, an alkylsulfonyl group, an arylsulfonyl        group, a heterocyclic sulfonyl group, an alkylsulfinyl group, an        arylsulfinyl group, a heterocyclic sulfinyl group, a sulfamoyl        group or a sulfo group, and the hydrogen atom of each        substituent may be substituted; and    -   R¹ and R⁵, or R⁵ and R⁶ may combine to form a 5- or 6-membered        ring.

The dye of formula (1) is described in more detail.

In formula (1), A represents a 5-membered heterocyclic group. Examplesof the heteroatom of the heterocyclic ring include N, O and S. A ispreferably a nitrogen-containing 5-membered heterocyclic ring and theheterocyclic ring may be condensed with an aliphatic ring, an aromaticring or another heterocyclic ring. Preferred examples of theheterocyclic ring represented by A include a pyrazole ring, an imidazolering, a thiazole ring, an isothiazole ring, a thiadiazole ring, abenzothiazole ring, a benzoxazole ring and a benzisothiazole ring. Eachheterocyclic group may further have a substituent. Among these rings,more preferred are a pyrazole ring, an imidazole ring, an isothiazolering, a thiadiazole ring and a benzothiazole ring represented by thefollowing formulae (a) to (f).

In formulae (a) to (f), R⁷ to R²⁰ each represents the same substituentas G, R¹ and R² in formula (1).

Among formulae (a) to (f), preferred are a pyrazole ring and anisothiazole ring represented by formulae (a) and (b), and most preferredis a pyrazole ring represented by formula (a).

In formula (1), B¹ and B² each represents ═CR¹— or —CR²═ or either oneof B¹ and B² represents a nitrogen atom and the other represents ═CR¹—or —CR²═. B¹ and B² each preferably represents ═CR¹— or —CR²═.

R⁵ and R⁶ each independently represents a hydrogen atom or asubstituent, the substituent is an aliphatic group, an aromatic group, aheterocyclic group, an acyl group, an alkoxycarbonyl group, anaryloxycarbonyl group, a carbamoyl group, an alkylsulfonyl group, anarylsulfonyl group or a sulfamoyl group, and the hydrogen atom of eachsubstituent may be substituted.

R⁵ and R⁶ each is preferably a hydrogen atom, an aliphatic group, anaromatic group, a heterocyclic group, an acyl group, an alkylsulfonylgroup or an arylsulfonyl group, more preferably a hydrogen atom, anaromatic group, a heterocyclic group, an acyl group, an alkylsulfonylgroup or an arylsulfonyl group, and most preferably a hydrogen atom, anaryl group or a heterocyclic group, and the hydrogen atom of eachsubstituent may be substituted, but R⁵ and R⁶ are not a hydrogen atom atthe same time.

G, R¹ and R² each independently represents a hydrogen atom or asubstituent, the substituent is a halogen atom, an aliphatic group, anaromatic group, a heterocyclic group, a cyano group, a carboxyl group, acarbamoyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, aheterocyclic oxycarbonyl group, an acyl group, a hydroxy group, analkoxy group, an aryloxy group, a heterocyclic oxy group, a silyloxygroup, an acyloxy group, a carbamoyloxy group, an alkoxycarbonyloxygroup, an aryloxycarbonyloxy group, an amino group, an acylamino group,a ureido group, a sulfamoylamino group, an alkoxycarbonylamino group, anaryloxycarbonylamino group, an alkylsulfonylamino group, anarylsulfonylamino group, a heterocyclic sulfonylamino group, a nitrogroup, an alkylthio group, an arylthio group, a heterocyclic thio group,an alkylsulfonyl group, an arylsulfonyl group, a heterocyclic sulfonylgroup, an alkylsulfinyl group, an arylsulfinyl group, a heterocyclicsulfinyl group, a sulfamoyl group or a sulfo group, and the hydrogenatom of each substituent may be substituted.

G is preferably a hydrogen atom, a halogen atom, an aliphatic group, anaromatic group, a hydroxy group, an alkoxy group, an aryloxy group, anacyloxy group, a heterocyclic oxy group, an amino group, an acylaminogroup, a ureido group, a sulfamoylamino group, an alkoxycarbonylaminogroup, an aryloxycarbonylamino group, an alkylthio group, an arylthiogroup or a heterocyclic thio group, more preferably a hydrogen atom, ahalogen atom, an alkyl group, a hydroxy group, an alkoxy group, anaryloxy group, an acyloxy group, an amino group or an acylamino group,and most preferably a hydrogen atom, an amino group (preferably ananilino group) or an acylamino group, and the hydrogen atom of eachsubstituent may be substituted.

R¹ and R² each is preferably a hydrogen atom, an alkyl group, a halogenatom, an alkoxycarbonyl group, a carboxyl group, a carbamoyl group, ahydroxy group, an alkoxy group or a cyano group, and the hydrogen atomof each substituent may be substituted.

R¹ and R⁵, or R⁵ and R⁶ may combine to form a 5- or 6-membered ring.

When A has a substituent or when the substituent R¹, R², R⁵, R⁶ or Gfurther has a substituent, examples of the substituent include thesubstituents described above for G, R¹ and R².

In the case where the dye of the present invention is a water-solubledye, the dye preferably further has an ionic hydrophilic group as asubstituent on any position of A, R¹, R², R⁵, R⁶ and G. Examples of theionic hydrophilic group as a substituent include a sulfo group, acarboxyl group, a phosphono group and a quaternary ammonium group. Amongthese ionic hydrophilic groups, preferred are a carboxyl group, aphosphono group and a sulfo group, more preferred are a carboxyl groupand a sulfo group. The carboxyl group, the phosphono group and the sulfogroup each may be in a salt state and examples of the counter ion forforming the salt include ammonium ion, alkali metal ions (e.g., lithiumion, sodium ion, potassium ion) and organic cations (e.g.,tetramethylammonium ion, tetramethylguanidium ion,tetramethylphosphonium).

The terms (substituents) used in the present invention are describedbelow. These terms each is common among different symbols in formula (1)and also in formula (1a) shown later.

The halogen atom includes a fluorine atom, a chlorine atom and a bromineatom.

The aliphatic group means an alkyl group, a substituted alkyl group, analkenyl group, a substituted alkenyl group, an alkynyl group, asubstituted alkynyl group, an aralkyl group and a substituted aralkylgroup. The “substituted” used for a “substituted alkyl group” and thelike in the present invention means that the hydrogen atom present in an“alkyl group” or the like is substituted, for example, by a substituentdescribed above for G, R¹ and R².

The aliphatic group may be branched or may form a ring. The number ofcarbon atoms in the aliphatic group is preferably from 1 to 20, morepreferably from 1 to 16. The aryl moiety in the aralkyl group and in thesubstituted aralkyl group is preferably a phenyl group or a naphthylgroup, more preferably a phenyl group. Examples of the aliphatic groupinclude a methyl group, an ethyl group, a butyl group, an isopropylgroup, a tert-butyl group, a hydroxyethyl group, a methoxyethyl group, acyanoethyl group, a trifluoromethyl group, a 3-sulfopropyl group, a4-sulfobutyl group, a cyclohexyl group, a benzyl group, a 2-phenethylgroup, a vinyl group and an allyl group.

The aromatic group means an aryl group and a substituted aryl group. Thearyl group is preferably a phenyl group or a naphthyl group, morepreferably a phenyl group. The number of carbon atoms in the aromaticgroup is preferably from 6 to 20, more preferably from 6 to 16.

Examples of the aromatic group include a phenyl group, a p-tolyl group,a p-methoxyphenyl group, an o-chlorophenyl group and anm-(3-sulfopropylamino)phenyl group.

The heterocyclic group includes a substituted heterocyclic group. In theheterocyclic group, the heterocyclic ring may be condensed with analiphatic ring, an aromatic ring or another heterocyclic ring. Theheterocyclic group is preferably a 5- or 6-membered heterocyclic group.Examples of the substituent of the substituted heterocyclic groupinclude an aliphatic group, a halogen atom, an alkylsulfonyl group, anarylsulfonyl group, an acyl group, an acylamino group, a sulfamoylgroup, a carbamoyl group and an ionic hydrophilic group. Examples of theheterocyclic group include a 2-pyridyl group, a 2-thienyl group, a2-thiazolyl group, a 2-benzothiazolyl group, a 2-benzoxazolyl group anda 2-furyl group.

The carbamoyl group includes a substituted carbamoyl group. Examples ofthe substituent therefor include an alkyl group. Examples of thecarbamoyl group include a methylcarbamoyl group and a dimethylcarbamoylgroup.

The alkoxycarbonyl group includes a substituted alkoxycarbonyl group.The alkoxycarbonyl group is preferably an alkoxycarbonyl group havingfrom 2 to 20 carbon atoms. Examples of the substituent of thesubstituted alkoxycarbonyl group include an ionic hydrophilic group.Examples of the alkoxycarbonyl group include a methoxycarbonyl group andan ethoxycarbonyl group.

The aryloxycarbonyl group includes a substituted aryloxycarbonyl group.The aryloxycarbonyl group is preferably an aryloxycarbonyl group havingfrom 7 to 20 carbon atoms. Examples of the substituent of thesubstituted aryloxycarbonyl group include an ionic hydrophilic group.Examples of the aryloxycarbonyl group include a phenoxycarbonyl group.

The heterocyclic oxycarbonyl group includes a substituted heterocyclicoxycarbonyl group. Examples of the heterocyclic ring include theheterocyclic rings described above for the heterocyclic group. Theheterocyclic oxycarbonyl group is preferably a heterocyclic oxycarbonylgroup having from 2 to 20 carbon atoms. Examples of the substituent ofthe substituted heterocyclic oxycarbonyl group include an ionichydrophilic group. Examples of the heterocyclic oxycarbonyl groupinclude a 2-pyridyloxycarbonyl group.

The acyl group includes a substituted acyl group. The acyl group ispreferably an acyl group having from 1 to 20 carbon atoms. Examples ofthe substituent of the substituted acyl group include an ionichydrophilic group. Examples of the acyl group include an acetyl groupand a benzoyl group.

The alkoxy group includes a substituted alkoxy group. The alkoxy groupis preferably an alkoxy group having from 1 to 20 carbon atoms. Examplesof the substituent of the substituted alkoxy group include an alkoxygroup, a hydroxyl group and an ionic hydrophilic group. Examples of thealkoxy group include a methoxy group, an ethoxy group, an isopropoxygroup, a methoxyethoxy group, a hydroxyethoxy group and a3-carboxypropoxy group.

The aryloxy group includes a substituted aryloxy group. The aryloxygroup is preferably an aryloxy group having from 6 to 20 carbon atoms.Examples of the substituent of the substituted aryloxy group include analkoxy group and an ionic hydrophilic group. Examples of the aryloxygroup include a phenoxy group, a p-methoxyphenoxy group and ano-methoxyphenoxy group.

The heterocyclic oxy group includes a substituted heterocyclic oxygroup. Examples of the heterocyclic ring include the heterocyclic ringsdescribed above for the heterocyclic group. The heterocyclic oxy groupis preferably a heterocyclic oxy group having from 2 to 20 carbon atoms.Examples of the substituent of the substituted heterocyclic oxy groupinclude an alkyl group, an alkoxy group and an ionic hydrophilic group.Examples of the heterocyclic oxy group include a 3-pyridyloxy group anda 3-thienyloxy group.

The silyloxy group is preferably a silyloxy group substituted by analiphatic or aromatic group having from 1 to 20 carbon atoms. Examplesof the silyloxy group include a trimethylsilyloxy group and adiphenylmethylsilyloxy group.

The acyloxy group includes a substituted acyloxy group. The acyloxygroup is preferably an acyloxy group having from 1 to 20 carbon atoms.Examples of the substituent of the substituted acyloxy group include anionic hydrophilic group. Examples of the acyloxy group include anacetoxy group and a benzoyloxy group.

The carbamoyloxy group includes a substituted carbamoyloxy group.Examples of the substituent therefor include an alkyl group. Examples ofthe carbamoyloxy group include an N-methylcarbamoyloxy group.

The alkoxycarbonyloxy group includes a substituted alkoxycarbonyloxygroup. The alkoxycarbonyloxy group is preferably an alkoxycarbonyloxygroup having from 2 to 20 carbon atoms. Examples of thealkoxycarbonyloxy group include a methoxycarbonyloxy group and anisopropoxy-carbonyloxy group.

The aryloxycarbonyloxy group includes a substituted aryloxycarbonyloxygroup. The aryloxycarbonyloxy group is preferably an aryloxycarbonyloxygroup having from 7 to 20 carbon atoms. Examples of thearyloxycarbonyloxy group include a phenoxycarbonyloxy group.

The amino group includes a substituted amino group. Examples of thesubstituent therefor include an alkyl group, an aryl group and aheterocyclic group, and the alkyl group, the aryl group and theheterocyclic group each may further have a substituent. The alkylaminogroup includes a substituted alkylamino group. The alkylamino group ispreferably an alkylamino group having from 1 to 20 carbon atoms.Examples of the substituent of the substituted alkylamino group includean ionic hydrophilic group. Examples of the alkylamino group include amethylamino group and a diethylamino group.

The arylamino group includes a substituted arylamino group. Thearylamino group is preferably an arylamino group having from 6 to 20carbon atoms. Examples of the substituent of the substituted arylaminogroup include a halogen atom and an ionic hydrophilic group. Examples ofthe arylamino group include a phenylamino group and a2-chlorophenylamino group.

The heterocyclic amino group includes a substituted heterocyclic aminogroup. Examples of the heterocyclic ring include the heterocyclic ringsdescribed above for the heterocyclic group. The heterocyclic amino groupis preferably a heterocyclic amino group having from 2 to 20 carbonatoms. Examples of the substituent of the substituted heterocyclic aminogroup include an alkyl group, a halogen atom and an ionic hydrophilicgroup.

The acylamino group includes a substituted acylamino group. Theacylamino group is preferably an acylamino group having from 2 to 20carbon atoms. Examples of the substituent of the substituted acylaminogroup include an ionic hydrophilic group. Examples of the acylaminogroup include an acetylamino group, a propionylamino group, abenzoylamino group, an N-phenylacetylamino group and a3,5-disulfobenzoylamino group.

The ureido group includes a substituted ureido group. The ureido groupis preferably a ureido group having from 1 to 20 carbon atoms. Examplesof the substituent of the substituted ureido group include an alkylgroup and an aryl group. Examples of the ureido group include a3-methylureido group, a 3,3-dimethylureido group and a 3-phenylureidogroup.

The sulfamoylamino group includes a substituted sulfamoylamino group.Examples of the substituent therefor include an alkyl group. Examples ofthe sulfamoylamino group include an N,N-dipropylsulfamoylamino group.

The alkoxycarbonylamino group includes a substituted alkoxycarbonylaminogroup. The alkoxycarbonylamino group is preferably analkoxycarbonylamino group having from 2 to 20 carbon atoms. Examples ofthe substituent of the substituted alkoxycarbonylamino group include anionic hydrophilic group. Examples of the alkoxycarbonylamino groupinclude an ethoxycarbonylamino group.

The aryloxycarbonylamino group includes a substitutedaryloxycarbonylamino group. The aryloxycarbonylamino group is preferablyan aryloxycarbonylamino group having from 7 to 20 carbon atoms. Examplesof the substituent of the substituted aryloxycarbonylamino group includean ionic hydrophilic group. Examples of the aryloxycarbonylamino groupinclude a phenoxycarbonylamino group.

The alkylsulfonylamino group and the arylsulfonylamino group include asubstituted alkylsulfonylamino group and a substituted arylsulfonylaminogroup, respectively. The alkylsulfonylamino group and thearylsulfonylamino group are preferably an alkylsulfonylamino grouphaving from 1 to 20 carbon atoms and an arylsulfonylamino group havingfrom 1 to 20 carbon atoms, respectively. Examples of the substituent ofthe substituted alkylsulfonylamino group and substitutedarylsulfonylamino group include an ionic hydrophilic group. Examples ofthe alkylsulfonylamino group and arylsulfonylamino group include amethylsufonylamino group, an N-phenyl-methylsulfonylamino group, aphenylsulfonylamino group and a 3-carboxyphenyl-sulfonylamino group.

The heterocyclic sulfonylamino group includes a substituted heterocyclicsulfonylamino group. Examples of the heterocyclic ring include theheterocyclic rings described above for the heterocyclic group. Theheterocyclic sulfonylamino group is preferably a heterocyclicsulfonylamino group having from 1 to 12 carbon atoms. Examples of thesubstituent of the substituted heterocyclic sulfonylamino group includean ionic hydrophilic group. Examples of the heterocyclic sulfonylaminogroup include a 2-thienylsulfonylamino group and a3-pyridylsulfonylamino group.

The alkylthio group, the arylthio group and the heterocyclic thio groupinclude a substituted alkylthio group, a substituted arylthio group anda substituted heterocyclic thio group, respectively. Examples of theheterocyclic ring include the heterocyclic rings described above for theheterocyclic group. The alkylthio group, the arylthio group and theheterocyclic thio group are preferably an alkylthio group having from 1to 20 carbon atoms, an arylthio group having from 1 to 20 carbon atomsand a heterocyclic thio group having from 1 to 20 carbon atoms,respectively. Examples of the substituent of the substituted alkylthiogroup, substituted arylthio group and substituted heterocyclic thiogroup include an ionic hydrophilic group. Examples of the alkylthiogroup, arylthio group and heterocyclic thio group include a methylthiogroup, a phenylthio group and a 2-pyridylthio group.

The alkylsulfonyl group and the arylsulfonyl group include a substitutedalkylsulfonyl group and a substituted arylsulfonyl group, respectively.Examples of the alkylsulfonyl group and arylsulfonyl group include amethylsulfonyl group and a phenylsulfonyl group.

The heterocyclic sulfonyl group includes a substituted heterocyclicsulfonyl group. Examples of the heterocyclic ring include theheterocyclic rings described above for the heterocyclic group. Theheterocyclic sulfonyl group is preferably a heterocyclic sulfonyl grouphaving from 1 to 20 carbon atoms. Examples of the substituent of thesubstituted heterocyclic sulfonyl group include an ionic hydrophilicgroup. Examples of the heterocyclic sulfonyl group include a2-thienylsulfonyl group and a 3-pyridylsulfonyl group.

The alkylsulfinyl group and the arylsulfinyl group include a substitutedalkylsulfinyl group and a substituted arylsulfinyl group, respectively.Examples of the alkylsulfinyl group and arylsulfinyl group include amethylsulfinyl group and a phenylsulfinyl group.

The heterocyclic sulfinyl group includes a substituted heterocyclicsulfinyl group. Examples of the heterocyclic ring include theheterocyclic rings described above for the heterocyclic group. Theheterocyclic sulfinyl group is preferably a heterocyclic sulfinyl grouphaving from 1 to 20 carbon atoms. Examples of the substituent of thesubstituted heterocyclic sulfinyl group include an ionic hydrophilicgroup. Examples of the heterocyclic sulfinyl group include a4-pyridylsulfinyl group.

The sulfamoyl group includes a substituted sulfamoyl group. Examples ofthe substituent therefor include an alkyl group. Examples of thesulfamoyl group include a dimethylsulfamoyl group and adi-(2-hydroxyethyl)sulfamoyl group.

Among the dyes represented by formula (1), particularly preferred is astructure represented by the following formula (1a):

In formula (1a), R¹, R², R⁵ and R⁶ have the same meanings as in formula(1).

R³ and R⁴ each independently represents a hydrogen atom or a substituentand the substituent is an aliphatic group, an aromatic group, aheterocyclic group, an acyl group, an alkoxycarbonyl group, anaryloxycarbonyl group, a carbamoyl group, an alkylsulfonyl group, anarylsulfonyl group or a sulfamoyl group. R³ and R⁴ each is preferably ahydrogen atom, an aromatic group, a heterocyclic group, an acyl group,an alkylsulfonyl group or an arylsulfonyl group, more preferably ahydrogen atom, an aromatic group or a heterocyclic group.

Z¹ represents an electron-withdrawing group having a Hammett'ssubstituent constant σp value of 0.20 or more. Z¹ is preferably anelectron-withdrawing group having a σp value of 0.30 or more, morepreferably 0.45 or more, still more preferably 0.60 to more, but the σpvalue preferably does not exceed 1.0. Specific preferred examples ofthis substituent include electron-withdrawing substituents describedlater. Among those, preferred are an acyl group having from 2 to 20carbon atoms, an alkyloxycarbonyl group having from 2 to 20 carbonatoms, a nitro group, a cyano group, an alkylsulfonyl group having from1 to 20 carbon atoms, an arylsulfonyl group having from 6 to 20 carbonatoms, a carbamoyl group having from 1 to 20 carbon atoms and ahalogenated alkyl group having from 1 to 20 carbon atoms, more preferredare a cyano group, an alkylsulfonyl group having from 1 to 20 carbonatoms and an arylsulfonyl group having from 6 to 20 carbon atoms, andmost preferred is a cyano group.

Z² represents a hydrogen atom or a substituent and the substituent is analiphatic group, an aromatic group or a heterocyclic group. Z² ispreferably an aliphatic group, more preferably an alkyl group havingfrom 1 to 6 carbon atoms.

Q represents a hydrogen atom or a substituent and the substituent is analiphatic group, an aromatic group or a heterocyclic group. Q ispreferably a group comprising a nonmetallic atom group necessary forforming a 5-, 6-, 7- or 8-membered ring. The 5-, 6-, 7- or 8-memberedring may be substituted, may be a saturated ring or may have anunsaturated bond. Q is more preferably an aromatic group or aheterocyclic group. Preferred examples of the nonmetallic atom include anitrogen atom, an oxygen atom, a sulfur atom and a carbon atom. Specificexamples of the ring structure include a benzene ring, a cyclopentanering, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, acyclohexene ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, apyridazine ring, a triazine ring, an imidazole ring, a benzimidazolering, an oxazole ring, a benzoxazole ring, a thiazole ring, abenzothiazole ring, an oxane ring, a sulfolane ring and a thiane ring.

The hydrogen atom of each substituent described in regard to formula(1a) may be substituted. Examples of the substituent include thesubstituents described in regard to formula (1), the groups described asexamples for G, R¹ and R², and ionic hydrophilic groups.

Here, the Hammett's substituent constant σp value used in the presentinvention is described. The Hammett's rule is an empirical ruleadvocated by L. P. Hammett in 1935 so as to quantitatively discuss theeffect of substituent on the reaction or equilibrium of benzenederivatives and its propriety is widely admitted at present. Thesubstituent constant determined by the Hammett's rule includes a σpvalue and a σm value and these values can be found in a large number ofgeneral publications but these are described in detail, for example, inJ. A. Dean (compiler), Lange's Handbook of Chemistry, 12th ed.,McGraw-Hill (1979), and Kagakuno Ryoiki (Chemistry Region), specialnumber, No. 122, pp. 96-103, Nankodo (1979). In the present invention,each substituent is limited or described by using the Hammett'ssubstituent constant σp but this does not mean that the substituent islimited only to those having a known value which can be found in theabove-described publications. Needless to say, the substituent includessubstituents of which σp value is not known in publications but whenmeasured based on the Hammett's rule, falls within the range specified.Furthermore, although formula (1a) of the present invention includesthose which are not a benzene derivative, the σp value is used as ameasure for showing the electron effect of the substituent irrespectiveof the substitution site. In the present invention, the σp value is usedin such a meaning.

Examples of the electron-withdrawing group having a Hammett'ssubstituent constant σp value of 0.60 or more include a cyano group, anitro group, an alkylsulfonyl group (e.g., methylsulfonyl) and anarylsulfonyl group (e.g., phenylsulfonyl).

Examples of the electron-withdrawing group having a Hammett's σp valueof 0.45 or more include, in addition to those described above, an acylgroup (e.g., acetyl), an alkoxycarbonyl group (e.g.,dodecyloxycarbonyl), an aryloxycarbonyl group (e.g.,m-chlorophenoxycarbonyl), an alkylsulfinyl group (e.g.,n-propylsulfinyl), an arylsulfinyl group (e.g., phenylsulfinyl), asulfamoyl group (e.g., N-ethylsulfamoyl, N,N-dimethylsulfamoyl) and ahalogenated alkyl group (e.g., trifluoromethyl).

Examples of the electron-withdrawing group having a Hammett'ssubstituent constant σp value of 0.30 or more include, in addition tothose described above, an acyloxy group (e.g., acetoxy), a carbamoylgroup (e.g., N-ethylcarbamoyl, N,N-dibutylcarbamoyl), a halogenatedalkoxy group (e.g., trifluoromethyloxy), a halogenated aryloxy group(e.g., pentafluorophenyloxy), a sulfonyloxy group (e.g.,methylsulfonyloxy), a halogenated alkylthio group (e.g.,difluoromethylthio), an aryl group substituted by two or moreelectron-withdrawing groups having a σp value of 0.15 or more (e.g.,2,4-dinitrophenyl, pentachloro-phenyl) and a heterocyclic ring (e.g.,2-benzoxazolyl, 2-benzothiazolyl, 1-phenyl-2-benzimidazolyl).

Specific examples of the electron-withdrawing group having a σp value of0.20 or more include, in addition to those described above, a halogenatom.

The preferred combination of substituents in the azo dye represented byformula (1) is described below. R⁵ and R⁶ each is preferably a hydrogenatom, an alkyl group, an aryl group, a heterocyclic group, a sulfonylgroup or an acyl group, more preferably a hydrogen atom, an aryl group,a heterocyclic group or a sulfonyl group, and most preferably a hydrogenatom, an aryl group or a heterocyclic group. However, R⁵ and R⁶ are nota hydrogen atom at the same time.

G is preferably a hydrogen atom, a halogen atom, an alkyl group, ahydroxyl group, an amino group or an acylamino group, more preferably ahydrogen atom, a halogen atom, an amino group or an acylamino group, andmost preferably a hydrogen atom, an amino group or an acylamino group.

A is preferably a pyrazole ring, an imidazole ring, an isothiazole ring,a thiadiazole ring or a benzothiazole ring, more preferably a pyrazolering or an isothiazole ring, and most preferably a pyrazole ring.

B¹ and B² each is preferably ═CR¹— or —CR²═, and R¹ and R² each ispreferably a hydrogen atom, an alkyl group, a halogen atom, a cyanogroup, a carbamoyl group, a carboxyl group, a hydroxyl group, an alkoxygroup or an alkoxycarbonyl group, more preferably a hydrogen atom, analkyl group, a carboxyl group, a cyano group or a carbamoyl group.

As for the preferred combination of substituents in the compoundrepresented by formula (1), a compound where at least one of varioussubstituents is the preferred group is preferred, a compound where alarger number of various substituents are the preferred groups is morepreferred, and a compound where all substituents are the preferredgroups is most preferred.

Specific examples of the azo dye represented by formula (1) are shown in(Table 1) to (Table 13) below, but the azo dye for use in the presentinvention is not limited to those shown below.

Dye R₁ R₂ R₃ a-1

a-2

a-3

a-4

a-5

a-6

a-7

a-8

a-9

C₈H₁₇(t) a-10

Dye R₁ R₂ R₃ R₄ a-11

a-12

a-13

a-14

a-15

a-16

a-17

Dye R₁ R₂ R₃ R₄ a-18

a-19

—SO₂CH₃

a-20

—COCH₃ C₈H₁₇(t) C₈H₁₇(t) a-21

—SO₂CH₃

C₈H₁₇(t) a-22

H

a-23

H

a-24

H

a-25

Dye R₁ R₂ R₃ R₄ a-26

a-27

a-28

a-29

a-30

C₈H₁₇(t) a-31

a-32

a-33

a-34

a-35

a-36

a-37

a-38

a-39

a-40

Dye R₁ R₂ R₃ R₄ R₅ R₆ R₇ R₈ a-41

CN

H CONH₂ SO₂CH₃

a-42

Br

COOEt H

C₈H₁₇(t) COCH₃ a-43

SO₂CH₃

CONH₂ H

a-44

CN

H H

SO₂CH₃ a-45

Br

H CONH₂

a-46

CN

CH₃ H

Dye R₁ R₂ R₃ R₄ R₅ R₆ b-1 CH₃ CH₃ CN H

b-2 CH₃ CH₃ CN H

b-3 CH₃ CH₃ CONH₂ H

b-4 CH₃ CH₃ H H

b-5 CH₃ H CN H

b-6 CH₃ CH₃ H

b-7 CH₃ CH₃ H

b-8 CH₃ H H SO₂CH₃

Dye R₁ R₂ R₃ R₄ R₅ R₆ c-1 —SCH₃ CH₃ CN H C₈H₁₇(t)

c-2

H CONH₂ H

c-3

CH₃ H

c-4 —CH₃ CH₃ H

c-5

H H

C₈H₁₇(t)

Dye R₁ R₂ R₃ R₄ R₅ R₆ d-1 Me CH₃ CN H

d-2 Me CH₃ CN H

d-3 Me H H

d-4 Ph CH₃ CONH₂ H

d-5 Ph CH₃ H

Dye R₁ R₂ R₃ R₄ R₅ R₆ e-1 5-Cl CH₃ CONH₂ H C₈H₁₇(t) C₈H₁₇(t) e-25,5-diCl H H

e-3 5,6-diCl CH₃ H

COCH₃ e-4 5-CH₃ H CN H

e-5 5-NO₂ CH₃ H SO₂CH₃

f-1

f-2

The inkjet recording ink of the present invention (sometimes alsoreferred to as “the ink of the present invention”) is obtained bydissolving or dispersing at least one of these azo dyes in an aqueousmedium and preferably contains the azo dye in an amount of 0.2 to 20mass %, more preferably from 0.5 to 15 mass %. The solubility in waterat 20° C. (or dispersion degree in a stable state) is preferably 5 mass% or more, more preferably 10 mass % or more.

The magenta dye having an azo group for use in the present invention hasan oxidation potential, in an aqueous medium for ink, nobler than 1.0 Vvs SCE, preferably nobler than 1.1 V vs SCE, more preferably nobler than1.2 V vs SCE. The potential can be elevated by selecting the preferredstructural features described above, more specifically, by selecting adye structure of a type having a chromophore represented by(heterocyclic ring A) —N═N— (heterocyclic ring B), selecting an azo dyein which an aromatic nitrogen-containing 6-membered heterocyclic ring isbonded as a coupling component directly to at least one side of the azogroup, and selecting an azo dye having an aromatic ring amino group- orheterocyclic amino group-containing structure as an auxochrome, andfurthermore by removing α hydrogen of the azo dye. In particular, thedye of formula (1) expresses a noble potential. This is specificallydescribed in Japanese Patent Application No. 2001-254878.

The oxidation potential of the azo dye is measured in the same manner asthat of the phthalocyanine dye which is described later.

[The oxidation potential as used herein can be measured by variousmeasuring methods such as direct current polarography which is a methodof measuring the oxidation potential in an aqueous solution orwater-mixed solvent system having dissolved therein the dye based on SCE(standard saturated calomel electrode) as the reference electrode and inwhich a graphite or platinum electrode is used as the working electrode,polarography in which a dropping mercury electrode is used, cyclicvoltammetry method (CV), rotating ring-disk electrode method and combelectrode method. The oxidation potential is specifically measured asfollows. A test sample is dissolved to a concentration of 1×10⁻⁴ to1×10⁻⁶ mol·dm⁻³ in a solvent such as dimethylformamide or acetonitrilecontaining a supporting electrolyte such as sodium perchlorate ortetrapropylammonium perchlorate and the oxidation potential is measuredas a value to SCE (standard saturated calomel electrode) by using theabove-described method. The supporting electrolyte and solvent used canbe appropriately selected according to the oxidation potential orsolubility of the test sample. The supporting electrolyte and solventwhich can be used are described in Akira Fujishima et al., DenkikagakuSokutei Ho (Electrochemical Measuring Method), pp. 101-118, GihodoShuppan Sha (1984).

The oxidation potential value sometimes deviates on the order of severaltens of millivolt due to the effect of, for example, liquid junctionpotential or liquid resistance of sample solution, but thereproducibility of measured potential value can be guaranteed by thecalibration using a standard sample (for example, hydroquinone) and thesame measured value can be obtained by any of those potential measuringmethods.]

Another basis for the oxidation resistance of the azo dye having anoxidation potential nobler than 1.0 V vs SCE is an enforceddiscoloration rate constant for ozone gas. The azo dye preferably has anenforced discoloration rate constant of 5.0×10⁻² [hour⁻¹] or less, morepreferably 3.0×10⁻² [hour⁻¹] or less, still more preferably 1.5×10⁻²[hour⁻¹] or less.

The enforced discoloration rate constant for ozone gas is determined asfollows. An image is printed on a reflective image-receiving medium byusing only the ink concerned and the colored region having a color inthe main spectral absorption region of the ink and having a reflectiondensity of 0.90 to 1.10 as measured through a Status A filter isselected as the initial density point. This initial density is definedas the starting density (=100%). Then, this image is discolored by usingan ozone discoloration tester capable of always keeping an ozoneconcentration of 5 mg/L, the time period until the density becomes 80%of the initial density is measured, a reciprocal [hour⁻¹] of this timeperiod is determined and on the assumption that the relationship betweenthe discoloration density and the time period follows the rate equationof first-order reaction, the value determined is used as thediscoloration reaction rate constant. Accordingly, the discolorationrate constant obtained is a discoloration rate constant in the coloredregion of an image printed by the ink, but in the present invention,this vale is used as the discoloration rate constant of the ink.

The test print patch may be a patch obtained by printing a black squaresymbol of JIS code 2223, a stepwise color patch of Macbeth chart, or anarbitrary stepwise density patch where the measured area can beobtained.

The reflection density of the reflection image (stepwise color patch)printed for measurement is a density determined with measurement lightthrough a Status A filter by a densitometer satisfying the InternationalStandard ISO5-4 (geometrical conditions for reflection density).

In the test chamber for the measurement of enforced discoloration rateconstant for ozone gas, an ozone generator (for example, in ahigh-voltage discharge system of applying an a.c. voltage to dry air)capable of constantly maintaining an internal ozone gas concentration of5 mg/L is provided and the exposure temperature is adjusted to 25° C.

This enforced discoloration rate constant is an index for showing thesusceptibility to oxidation by oxidative atmosphere in the environment,such as photochemical smog, exhaust gas of automobiles, organic vaporfrom painted furniture surface or carpet, or gas generated from theframe interior in a bright room, and this is an index using ozone gas asa representative of such oxidative atmosphere.

The color hue of the magenta ink is described below. The magenta inkpreferably has λmax of 500 to 580 nm in view of color hue, morepreferably a small half-value width in the long-wave and short-wavesides of the maximum absorption wavelength, namely, sharp absorption.This is specifically described in JP-A-2002-309133. The sharp absorptioncan be also realized by introducing a methyl group into the α position.

The phthalocyanine dye which is the cyanine dye for use in the presentinvention is described in detail below.

As a result of intensive investigations on the inkjet recording ink, thepresent inventors have found that the properties required of the cyandye are 1) to give a good color hue and be free of change in the colorhue (solvate), 2) to exhibit excellent fastness (to light, ozone, NOx,solvent, oil and water), 3) to be safe (not carcinogenic by AMES, notirritating to skin and easily degradable), 4) to be inexpensive, 5) tohave high ε, 6) to be highly soluble, and 7) to have strong fixingproperty to a medium.

The properties required of the ink and conc. ink are 1) to be uniformirrespective of the temperature and aging, 2) to be less contaminated,3) to exhibit good penetration into a medium, 4) to be uniform in thehitting size, 5) to be usable for all types of paper, 6) to be easilyprepared, 7) to ensure no ejection error, less bubbling and easydefoaming, and 8) to be stably ejected.

The properties required of the image is 1) to be clear without blurring,discoloration and beading, 2) to have scratch resistance, 3) to havehigh and uniform gloss, 4) to have good image preservability andexcellent balance in discoloration, 5) to be quickly dried, 6) to beprinted at a high speed, and 7) to have no image density dependency inthe discoloration ratio.

The properties required of the inkjet recording ink is to be excellentin both light fastness and ozone resistance and small in the change ofcolor hue and surface state (less generation of bronze and lessprecipitation of dye). As for the light fastness (OD1.0), the lightfastness with a TAC filter on Epson PM Photographic Image-ReceivingPaper by Xe of 1.1 W/m (intermittent conditions) is preferably 90% ormore in terms of the residual color ratio for 3 days. Also, the coloringmatter residual ratio for 14 days is preferably 85% or more. As for theozone resistance, the ozone resistance (OD1.0) under the condition of 5ppm or less of ozone is preferably 60% or more, more preferably 70% ormore, still more preferably 80% or more, in terms of the coloring matterresidual ratio for one day. Also, the coloring matter residual ratio for5 days is preferably 25% or more, more preferably 40% or more, stillmore preferably 50% or more. Samples varied in the coated amount of dyeare prepared by GTC and the amount of Cu element contained in the dye ismeasured by a fluorescent X ray.

The Cu ion is present in the form of a phthalate as a result ofdecomposition of the phthalocyanine dye. The amount of Cu salt presentin an actual print is preferably 10 mg/m² or less in terms of Cu ion.The amount of Cu flowed out from the print is determined by forming anentire cyan solid image having a Cu salt amount of 20 mg/m² or less interms of Cu ion, discoloring this image with ozone and analyzing theamount of ion flowed out into water. Incidentally, all Cu compounds aretrapped by the image-receiving material before the discoloration. Theamount of Cu ion flowed out into water is preferably 20% or less of alldyes.

It has been found in the present invention that a phthalocyanine dyehaving such properties can be obtained, for example, by 1) elevating theoxidation potential, 2) enhancing the aggregating property, 3)introducing an aggregation accelerating group, intensifying the hydrogenbond at the time of π-π stacking, or 4) not incorporating a substituentat the α-position, that is, facilitating the stacking.

Conventional phthalocyanine dyes used for the inkjet ink are derivedfrom an unsubstituted phthalocyanine through sulfonation and these are amixture which cannot be specified in the number and positions ofsubstituents. On the other hand, the dye for use in the inkjet recordingink of the present invention is a phthalocyanine dye which can bespecified in the number and positions of substituents. The firststructural feature is that the dye is a water-soluble phthalocyanine dyeobtained by not passing through sulfonation of an unsubstitutedphthalocyanine. The second structural feature is that the dye has anelectron-withdrawing group at the β-position of a benzene ring ofphthalocyanine, preferably at the β-position of all benzene rings.Specific examples of useful dyes include those where a sulfonyl group issubstituted (see, Japanese Patent Application Nos. 2001-47013 and2001-190214), a sulfamoyl group in general is substituted (see, JapanesePatent Application Nos. 2001-24352 and 2001-189982), a heterocyclicsulfamoyl group is substituted (see, Japanese Patent Application Nos.2001-96610 and 2001-190216), a heterocyclic sulfonyl group issubstituted (see, Japanese Patent Application Nos. 2001-76689 and2001-190215), a specific sulfamoyl group is substituted (see, JapanesePatent Application No. 2001-57063), a carbonyl group is substituted(see, Japanese Patent Application No. 2002-012869), or the dye has aspecific substituent for enhancing the solubility or ink stability orpreventing the bronze phenomenon, such as asymmetric carbon (see,Japanese Patent Application No. 2002-012868) or Li salt form (see,Japanese Patent Application No. 2002-012864).

The first physical feature of the dye for use in the inkjet recordingink of the present invention is to have a high oxidation potential. Theoxidation potential is preferably nobler than 1.00 V, more preferablynobler than 1.1 V, and most preferably nobler than 1.2 V. The secondphysical feature is to have a strong aggregating property. Specificexamples of the dye having this property include those where theaggregation of oil-soluble dyes is specified (see, Japanese PatentApplication No. 2001-64413) or the aggregation of water-soluble dyes isspecified (see, Japanese Patent Application No. 2001-117350).

With respect to the relationship between the number of aggregatinggroups and the performance (light absorbance of ink), when anaggregating group is introduced, reduction of light absorbance orshifting of λmax to the shorter wave is liable to occur even in a dilutesolution. With respect to the relationship between the number ofaggregating groups and the performance (reflection OD on Epson PM920Image-Receiving Paper), as the number of aggregating groups increases,the reflection OD with the same ion intensity more decreases. That is,the aggregation is considered to proceed on the image-receiving paper.With respect to the relationship between the number of aggregatinggroups and the performance (ozone resistance/light fastness), as thenumber of aggregating groups increases, the ozone resistance is moreenhanced. A dye having a large number of aggregating groups tends to beenhanced also in the light fastness. In order to impart the ozoneresistance, the above-described substituent X (which represents X₁, X₂,X₃, X₄ or the like) must be present. The reflection OD and the fastnessare in the trade-off relationship and therefore, it is necessary toenhance the light fastness without weakening the aggregation.

Preferred embodiments of the ink (composition) of the present inventionare:

-   -   1) a cyan ink where the light fastness with a TAC filter on        Epson PM Photographic Image-Receiving Paper by Xe of 1.1 W/m        (intermittent conditions) is 90% or more in terms of the        residual color ratio for 3 days;    -   2) a cyan ink where after storage in an ozone environment of 5        ppm for 24 hours, the monochromatic moiety printed by using a        single (cyan) color of the ink to give a cyan reflection density        of 0.9 to 1.1 in a Status A filter has a coloring matter        residual ratio (density after discoloration/initial density×100)        of 60% (preferably 80%) or more;    -   3) a cyan ink where after discoloration with ozone under the        conditions of 2 above, the amount of Cu ion flowed out into        water is 20% or less of all dyes; and    -   4) a cyan ink having penetrability such that the amount of ink        penetrated into a specific image-receiving paper is 30% or more        of the upper portion of the image-receiving layer.

The dye contained in the inkjet recording ink composition of the presentinvention is a phthalocyanine dye, preferably a water-soluble dye havingan oxidation potential nobler than 1.0, more preferably a dye havingozone gas fastness satisfying the above-described conditions, still morepreferably a phthalocyanine dye represented by formula (I).

The phthalocyanine dye is a dye having fastness but this dye is known tobe inferior in the fastness to ozone gas when used as a coloring matterfor inkjet recording.

In the present invention, an electron-withdrawing group is preferablyintroduced into the phthalocyanine skeleton to render the oxidationpotential nobler than 1.0 V (vs SCE) and thereby reduce the reactivitywith ozone which is an electrophilic agent. A nobler oxidation potentialis more preferred and the oxidation potential is more preferably noblerthan 1.1 V (vs SCE) and most preferably nobler than 1.2 V (vs SCE).

The oxidation potential value (Eox) can be easily measured by oneskilled in the art and the method therefor is described, for example, inP. Delahay, New Instrumental Methods in Electrochemistry, IntersciencePublishers (1954), A. J. Bard et al., Electrochemical Methods, JohnWiley & Sons (1980), and Akira Fujishima et al., Denkikagaku Sokutei Ho(Electrochemical Measuring Method), Gihodo Shuppan Sha (1984).

More specifically, a test sample is dissolved to a concentration of1×10⁻⁴ to 1×10⁻⁶ mol/liter in a solvent such as dimethylformamide oracetonitrile containing a supporting electrolyte such as sodiumperchlorate or tetrapropylammonium perchlorate and the oxidationpotential is measured as a value to SCE (saturated calomel electrode) byusing a cyclic voltammetry or a direct current polarography. This valuesometimes deviates on the order of several tens of millivolt due to theeffect of, for example, liquid junction potential or liquid resistanceof sample solution, but the reproducibility of potential can beguaranteed by adding a standard sample (for example, hydroquinone).

In order to univocally specify the potential, in the present invention,the value (vs SCE) measured by a direct current polarography in adimethylformamide (concentration of dye: 0.001 mol dm⁻³) containing 0.1mol dm⁻³ of tetrapropylammonium perchlorate as the supportingelectrolyte is used as the oxidation potential of the dye.

The Eox (oxidation potential) value indicates the transferability of anelectron from the sample to the electrode and as the value is larger(the oxidation potential is nobler), the electron is less transferablefrom the sample to the electrode, in other words, the oxidation lessoccurs. As for the relationship with the structure of compound, theoxidation potential becomes nobler when an electron-withdrawing group isintroduced, and becomes baser when an electron-donating group isintroduced. In the present invention, the oxidation potential ispreferably rendered nobler by introducing an electron-withdrawing groupinto the phthalocyanine skeleton so as to reduce the reactivity withozone which is an electrophilic agent. When the Hammett's substituentconstant σp value as a measure for the electron-withdrawing property orelectron-donating property of substituent is used, the oxidationpotential can be rendered nobler by introducing a substituent having alarge σp value, such as sulfinyl group, sulfonyl group and sulfamoylgroup.

Also for the purpose of such potential control, the phthalocyanine dyerepresented by formula (I) is preferably used.

The phthalocyanine dye having the above-described oxidation potential isapparently a cyanine dye excellent in both the light fastness and theozone resistance, because this dye satisfies those conditions for lightfastness and ozone resistance.

The phthalocyanine dye (preferably the phthalocyanine dye represented byformula (I)) for use in the present invention is described in detailbelow.

In formula (I), X₁, X₂, X₃ and X₄ each independently represents —SO-Z,—SO₂-Z, —SO₂NR1R2, a sulfo group, —CONR1R2 or —CO₂R1. Among thesesubstituents, preferred are —SO-Z, —SO₂-Z, —SO₂NR1R2 and —CONR1R2, morepreferred are —SO₂-Z and —SO₂NR1R2, and most preferred is —SO₂-Z. In thecase where a₁ to a₄ showing the number of substituents each represents anumber of 2 or more, a plurality of substituents X₁, X₂, X₃ or X₄ may bethe same or different and each independently represents any one of theabove-described groups. X₁, X₂, X₃ and X₄ may be completely the samesubstituents, may be substituents of the same kind but partiallydifferent as in the case, for example, where X₁, X₂, X₃ and X₄ all are—SO₂-Z and Zs are different from each other, or may contain substituentsdifferent from each other, for example, —SO₂-Z and —SO₂NR1R2.

Each Z independently represents a substituted or unsubstituted alkylgroup, a substituted or unsubstituted cycloalkyl group, a substituted orunsubstituted alkenyl group, a substituted or unsubstituted aralkylgroup, a substituted or unsubstituted aryl group, or a substituted orunsubstituted heterocyclic group, preferably a substituted orunsubstituted alkyl group, a substituted or unsubstituted aryl group ora substituted or unsubstituted heterocyclic group, and most preferably asubstituted alkyl group, a substituted aryl group or a substitutedheterocyclic group.

R1 and R2 each independently represents a hydrogen atom, a substitutedor unsubstituted alkyl group, a substituted or unsubstituted cycloalkylgroup, a substituted or unsubstituted alkenyl group, a substituted orunsubstituted aralkyl group, a substituted or unsubstituted aryl group,or a substituted or unsubstituted heterocyclic group, preferably ahydrogen atom, a substituted or unsubstituted alkyl group, a substitutedor unsubstituted aryl group, or a substituted or unsubstitutedheterocyclic group, more preferably a hydrogen atom, a substituted alkylgroup, a substituted aryl group or a substituted heterocyclic group.However, it is not preferred that R1 and R2 both are a hydrogen atom.

The substituted or unsubstituted alkyl group represented by R1, R2 and Zis preferably an alkyl group having from 1 to 30 carbon atoms, morepreferably a branched alkyl group because the solubility of dye and thestability of ink are improved, still more preferably an alkyl grouphaving an asymmetric carbon (use in the racemic form). Examples of thesubstituent include those described later as the substituent when Z, R1,R2, Y₁, Y₂, Y₃ and Y₄ can further have a substituent. In particular, ahydroxyl group, an ether group, an ester group, a cyano group, an amidogroup and a sulfonamido group are preferred because the aggregatingproperty and fastness of dye are enhanced. Other than these, the alkylgroup may be substituted by a halogen atom or an ionic hydrophilicgroup. Incidentally, the number of carbon atoms in the alkyl group doesnot contain carbon atoms of substituents and this applies to othergroups.

The substituted or unsubstituted cycloalkyl group represented by R1, R2and Z is preferably a cycloalkyl group having from 5 to 30 carbon atoms,more preferably a cycloalkyl group having an asymmetric carbon (use inthe racemic form) because the solubility of dye and the stability of inkare improved. Examples of the substituent include those described lateras the substituent when Z. R1, R2, Y₁, Y₂, Y₃ and Y₄ can further have asubstituent. In particular, a hydroxyl group, an ether group, an estergroup, a cyano group, an amido group and a sulfonamido group arepreferred because the aggregating property and fastness of dye areenhanced. Other than these, the cycloalkyl group may be substituted by ahalogen atom or an ionic hydrophilic group.

The substituted or unsubstituted alkenyl group represented by R1, R2 andZ is preferably an alkenyl group having from 2 to 30 carbon atoms, morepreferably a branched alkenyl group because the solubility of dye andthe stability of ink are improved, still more preferably an alkenylgroup having an asymmetric carbon (use in the racemic form). Examples ofthe substituent include those described later as the substituent when Z,R1, R2, Y₁, Y₂, Y₃ and Y₄ can further have a substituent. In particular,a hydroxyl group, an ether group, an ester group, a cyano group, anamido group and a sulfonamido group are preferred because theaggregating property and fastness of dye are enhanced. Other than these,the alkenyl group may be substituted by a halogen atom or an ionichydrophilic group.

The substituted or unsubstituted aralkyl group represented by R1, R2 andZ is preferably an aralkyl group having from 7 to 30 carbon atoms, morepreferably a branched aralkyl group because the solubility of dye andthe stability of ink are improved, still more preferably an aralkylgroup having an asymmetric carbon (use in the racemic form). Examples ofthe substituent include those described later as the substituent when Z,R1, R2, Y₁, Y₂, Y₃ and Y₄ can further have a substituent. In particular,a hydroxyl group, an ether group, an ester group, a cyano group, anamido group and a sulfonamido group are preferred because theaggregating property and fastness of dye are enhanced. Other than these,the aralkyl group may be substituted by a halogen atom or an ionichydrophilic group.

The substituted or unsubstituted aryl group represented by R1, R2 and Zis preferably an aryl group having from 6 to 30 carbon atoms. Examplesof the substituent include those described later as the substituent whenZ, R1, R2, Y₁, Y₂, Y₃ and Y₄ can further have a substituent. Inparticular, an electron-withdrawing group is preferred because the dyecan have a noble oxidation potential and can be improved in thefastness. Examples of the electron-withdrawing group include thosehaving a positive Hammett's substituent constant σp value. Among these,preferred are a halogen atom, a heterocyclic group, a cyano group, acarboxyl group, an acylamino group, a sulfonamido group, a sulfamoylgroup, a carbamoyl group, a sulfonyl group, an imido group, an acylgroup, a sulfo group and a quaternary ammonium group, more preferred area cyano group, a carboxyl group, a sulfamoyl group, a carbamoyl group, asulfonyl group, an imido group, an acyl group, a sulfo group and aquaternary ammonium group.

The heterocyclic group represented by R1, R2 and Z is preferably a 5- or6-membered ring and the ring may be further condensed. Also, theheterocyclic group may be an aromatic heterocyclic group or anon-aromatic heterocyclic group. Examples of the heterocyclic grouprepresented by R1, R2 and Z are shown below in the form of aheterocyclic ring by omitting the substitution site. The substitutionsite is not limited and, for example, in the case of pyridine, the2-position, 3-position and 4-position can be substituted. Examplesinclude pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline,isoquinoline, quinazoline, cinnoline, phthalazine, quinoxaline, pyrrole,indole, furan, benzofuran, thiophene, benzothiophene, pyrazole,imidazole, benzimidazole, triazole, oxazole, benzoxazole, thiazole,benzothiazole, isothiazole, benzisothiazole, thiadiazole, isoxazole,benzisoxazole, pyrrolidine, piperidine, piperazine, imidazolidine andthiazoline. In particular, an aromatic heterocyclic group is preferred.Preferred examples thereof include, shown in the same manner as above,pyridine, pyrazine, pyrimidine, pyridazine, triazine, pyrazole,imidazole, benzimidazole, triazole, thiazole, benzothiazole,isothiazole, benzisothiazole and thiadiazole. These groups each may havea substituent and examples of the substituent include those describedlater as the substituent when Z, R1, R2, Y₁, Y₂, Y₃ and Y₄ can furtherhave a substituent. Preferred substituents are the same as theabove-described substituents of the aryl group and more preferredsubstituents are the same as the above-described more preferredsubstituents of the aryl group.

Y₁, Y₂, Y₃ and Y₄ each independently represents a hydrogen atom, ahalogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, anaralkyl group, an aryl group, a heterocyclic group, a cyano group, ahydroxyl group, a nitro group, an amino group, an alkylamino group, analkoxy group, an aryloxy group, an acylamino group, an arylamino group,a ureido group, a sulfamoylamino group, an alkylthio group, an arylthiogroup, an alkoxycarbonylamino group, a sulfonamido group, a carbamoylgroup, a sulfamoyl group, a sulfonyl group, an alkoxycarbonyl group, aheterocyclic oxy group, an azo group, an acyloxy group, a carbamoyloxygroup, a silyloxy group, an aryloxycarbonyl group, anaryloxycarbonylamino group, an imido group, a heterocyclic thio group, aphosphoryl group, an acyl group, a carboxyl group or a sulfo group.These groups each may further have a substituent.

Y₁, Y₂, Y₃ and Y₄ each is preferably a hydrogen atom, a halogen atom, analkyl group, an aryl group, a cyano group, an alkoxy group, an amidogroup, a ureido group, a sulfonamido group, a carbamoyl group, asulfamoyl group, an alkoxycarbonyl group, a carboxyl group or a sulfogroup, more preferably a hydrogen atom, a halogen atom, a cyano group, acarboxyl group or a sulfo group, and most preferably a hydrogen atom.

When Z, R1, R2, Y₁, Y₂, Y₃ and Y₄ each is a group which can further havea substituent, the group may further have a substituent described below.

Examples of the substituent include a linear or branched alkyl grouphaving from 1 to 12 carbon atoms, a linear or branched aralkyl grouphaving from 7 to 18 carbon atoms, a linear or branched alkenyl grouphaving from 2 to 12 carbon atoms, a linear or branched alkynyl grouphaving from 2 to 12 carbon atoms, a linear or branched cycloalkyl grouphaving from 3 to 12 carbon atoms, a linear or branched cycloalkenylgroup having from 3 to 12 carbon atoms (these groups each is preferablya group having a branched chain because the solubility of dye and thestability of ink are improved, more preferably a group having anasymmetric carbon; specific examples of the groups include methyl,ethyl, propyl, isopropyl, sec-butyl, tert-butyl, 2-ethylhexyl,2-methylsulfonylethyl, 3-phenoxypropyl, trifluoromethyl andcyclopentyl), a halogen atom (e.g., chlorine, bromine), an aryl group(e.g., phenyl, 4-tert-butylphenyl, 2,4-di-tert-amylphenyl), aheterocyclic group (e.g., imidazolyl, pyrazolyl, triazolyl, 2-furyl,2-thienyl, 2-pyrimidinyl, 2-benzothiazolyl), a cyano group, a hydroxylgroup, a nitro group, a carboxy group, an amino group, an alkyloxy group(e.g., methoxy, ethoxy, 2-methoxyethoxy, 2-methanesulfonylethoxy), anaryloxy group (e.g., phenoxy, 2-methylphenoxy, 4-tert-butylphenoxy,3-nitrophenoxy, 3-tert-butyloxycarbamoylphenoxy, 3-methoxycarbamoyl), anacylamino group (e.g., acetamido, benzamido,4-(3-tert-butyl-4-hydroxyphenoxy)butanamido), an alkylamino group (e.g.,methylamino, butylamino, diethylamino, methylbutylamino), an anilinogroup (e.g., phenylamino, 2-chloroanilino), a ureido group (e.g.,phenylureido, methylureido, N,N-dibutylureido), a sulfamoylamino group(e.g., N,N-dipropylsulfamoylamino), an alkylthio group (e.g.,methylthio, octylthio, 2-phenoxyethylthio), an arylthio group (e.g.,phenylthio, 2-butoxy-5-tert-octylphenylthio, 2-carboxyphenylthio), analkyloxycarbonylamino group (e.g., methoxycarbonylamino), a sulfonamidogroup (e.g., methanesulfonamido, benzene-sulfonamido,p-toluenesulfonamido), a carbamoyl group (e.g., N-ethylcarbamoyl,N,N-dibutylcarbamoyl), a sulfamoyl group (e.g., N-ethylsulfamoyl,N,N-dipropylsulfamoyl, N-phenylsulfamoyl), a sulfonyl group (e.g.,methanesulfonyl, octanesulfonyl, benzenesulfonyl, toluenesulfonyl), analkyloxycarbonyl group (e.g., methoxycarbonyl, butyloxy-carbonyl), aheterocyclic oxy group (e.g., 1-phenyltetrazol-5-oxy,2-tetrahydropyranyloxy), an azo group (e.g., phenylazo,4-methoxyphenylazo, 4-pivaloylamino-phenylazo,2-hydroxy-4-propanoylphenylazo), an acyloxy group (e.g., acetoxy), acarbamoyloxy group (e.g., N-methylcarbamoyloxy, N-phenylcarbamoyloxy), asilyloxy group (e.g., trimethylsilyloxy, dibutylmethylsilyloxy), anaryloxycarbonylamino group (e.g., phenoxycarbonylamino), an imido group(e.g., N-succinimido, N-phthalimido), a heterocyclic thio group (e.g.,2-benzothiazolylthio, 2,4-di-phenoxy-1,3,5-triazole-6-thio,2-pyridylthio), a sulfinyl group (e.g., 3-phenoxypropylsulfinyl), aphosphonyl group (e.g., phenoxyphosphonyl, octyloxy-phosphonyl,phenylphosphonyl), an aryloxycarbonyl group (e.g., phenoxycarbonyl), anacyl group (e.g., acetyl, 3-phenylpropanoyl, benzoyl), and an ionichydrophilic group (e.g., carboxyl, sulfo, phosphono, quaternaryammonium).

In the case where the phthalocyanine dye represented by formula (I) iswater-soluble, the dye preferably contains an ionic hydrophilic group.Examples of the ionic hydrophilic group include a sulfo group, acarboxyl group, a phosphono group and a quaternary ammonium group. Amongthese ionic hydrophilic groups, preferred are a carboxyl group, aphosphono group and a sulfo group, more preferred are a carboxyl groupand a sulfo group. The carboxyl group, the phosphono group and the sulfogroup each may be in a salt state and examples of the counter ion forforming the salt include ammonium ion, alkali metal ions (e.g., lithiumion, sodium ion, potassium ion) and organic cations (e.g.,tetramethylammonium ion, tetramethylguanidium ion,tetramethylphosphonium). Among these counter ions, alkali metal saltsare preferred and a lithium salt is more preferred because thesolubility of dye and the stability of ink are enhanced.

As for the number of ionic hydrophilic groups, the phthalocyanine dyepreferably contains at least two ionic hydrophilic groups, morepreferably at least two sulfo groups and/or carboxyl groups, within onemolecule.

a₁ to a₄ and b₁ to b₄ represent the number of substituents X₁ to X₄ andY₁ to Y₄, respectively. a₁ to a₄ each independently represents aninteger of 0 to 4 but all are not 0 at the same time. b₁ to b₄ eachindependently represents an integer of 0 to 4. When a₁, a₂, a₃, a₄, b₁,b₂, b₃ or b₄ represents an integer of 2 or more, a plurality of X₁s,X₂s, X₃s, X₄s, Y₁S, Y₂S, Y₃S or Y₄s are present and these may be thesame or different.

a₁ and b₁ satisfy the relationship of a₁+b₁=4. In particular, acombination that a₁ represents 1 or 2 and b₁ represents 3 or 2 ispreferred, and a combination that a₁ represents 1 and b₁ represents 3 ismost preferred.

The same relationship as that between a₁ and b₁ is present in each ofthe pairs a₂ and b₂, a₃ and b₃, and a₄ and b₄, and the preferredcombination is also the same.

M represents a hydrogen atom, a metal element or an oxide, hydroxide orhalide thereof.

M is preferably a hydrogen atom, a metal element such as Li, Na, K, Mg,Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt,Cu, Ag, Au, Zn, Cd, Hg, Al, Ga, In, Si, Ge, Sn, Pb, Sb and Bi, an oxidesuch as VO and GeO, a hydroxide such as Si(OH)₂, Cr(OH)₂ and Sn(OH)₂, ora halide such as AlCl, SiCl₂, VCl, VCl₂, VOCl, FeCl, GaCl and ZrCl, morepreferably Cu, Ni, Zn or Al, and most preferably Cu.

Also, Pc (phthalocyanine ring) may form a dimer (for example,Pc-M-L-M-Pc) or a trimer through L (divalent linking group). At thistime, Ms may be the same or different.

The divalent linking group represented by L is preferably an oxy group—O—, a thio group —S—, a carbonyl group —CO—, a sulfonyl group —SO₂—, animino group —NH—, a methylene group —CH₂— or a group formed by combiningtwo or more of these groups.

As for the preferred combination of substituents in the compoundrepresented by formula (I), a compound where at least one of varioussubstituents is the preferred group is preferred, a compound where alarger number of various substituents are the preferred groups is morepreferred, and a compound where all substituents are the preferredgroups is most preferred.

Among the phthalocyanine dyes represented by formula (I), aphthalocyanine dye having a structure represented by formula (II) ispreferred. The phthalocyanine dye represented by formula (II) of thepresent invention is described in detail below.

In formula (II), X₁₁ to X₁₄ and Y₁₁ to Y₁₈ have the same meanings as X₁to X₄ and Y₁ to Y₄ in formula (I), respectively, and preferred examplesare also the same. M₁ has the same meaning as M in formula (I) andpreferred examples are also the same.

In formula (II), a₁₁ to a₁₄ each independently represents an integer of1 or 2 and preferably satisfy 423 a₁₁+a₁₂+a₁₃+a₁₄≦6, anda₁₁=a₁₂=a₁₃=a₁₄=1 is more preferred.

X₁₁, X₁₂, X₁₃ and X₁₄ may be completely the same substituents, may besubstituents of the same kind but partially different as in the case,for example, where X₁₁, X₁₂, X₁₃ and X₁₄ all are —SO₂-Z and Zs aredifferent from each other, or may contain substituents different fromeach other, for example, —SO₂-Z and —SO₂NR1R2.

In the phthalocyanine dye represented by formula (II), the followingcombinations of substituents are particularly preferred.

X₁₁ to X₁₄ each independently represents preferably —SO-Z, —SO₂-Z,—SO₂NR1R2 or —CONR1R2, more preferably —SO₂-Z or —SO₂NR1R2, and mostpreferably —SO₂-Z.

Each Z independently represents preferably a substituted orunsubstituted alkyl group, a substituted or unsubstituted aryl group ora substituted or unsubstituted heterocyclic group, and most preferably asubstituted alkyl group, a substituted aryl group or a substitutedheterocyclic group. In particular, the case where an asymmetric carbonis present in the substituent (use in the racemic form) is preferredbecause the solubility of dye and the stability of ink are enhanced.Also, the case where a hydroxyl group, an ether group, an ester group, acyano group, an amido group or a sulfonamido group is present in thesubstituent is preferred because the aggregating property and fastnessare improved.

R1 and R2 each independently represents preferably a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedaryl group or a substituted or unsubstituted heterocyclic group, morepreferably a hydrogen atom, a substituted alkyl group, a substitutedaryl group or a substituted heterocyclic group. However, it is notpreferred that R1 and R2 both are a hydrogen atom. In particular, thecase where an asymmetric carbon is present in the substituent (use inthe racemic form) is preferred because the solubility of dye and thestability of ink are enhanced. Also, the case where a hydroxyl group, anether group, an ester group, a cyano group, an amido group or asulfonamido group is present in the substituent is preferred because theaggregating property and fastness are improved.

Y₁₁ to Y₁₈ each independently represents preferably a hydrogen atom, ahalogen atom, an alkyl group, an aryl group, a cyano group, an alkoxygroup, an amido group, a ureido group, a sulfonamido group, a carbamoylgroup, a sulfamoyl group, an alkoxycarbonyl group, a carboxyl group or asulfo group, more preferably a hydrogen atom, a halogen atom, a cyanogroup, a carboxyl group or a sulfo group, and most preferably a hydrogenatom.

-   -   a₁₁ to a₁₄ each independently represents preferably 1 or 2 and        it is more preferred that all are 1.

M₁ represents a hydrogen atom, a metal element or an oxide, hydroxide orhalide thereof, preferably Cu, Ni, Zn or Al, and most preferably Cu.

In the case where the phthalocyanine dye represented by formula (II) iswater-soluble, the dye preferably contains an ionic hydrophilic group.Examples of the ionic hydrophilic group include a sulfo group, acarboxyl group, a phosphono group and a quaternary ammonium group. Amongthese ionic hydrophilic groups, preferred are a carboxyl group, aphosphono group and a sulfo group, more preferred are a carboxyl groupand a sulfo group. The carboxyl group, the phosphono group and the sulfogroup each may be in a salt state and examples of the counter ion forforming the salt include ammonium ion, alkali metal ions (e.g., lithiumion, sodium ion, potassium ion) and organic cations (e.g.,tetramethylammonium ion, tetramethylguanidium ion,tetramethylphosphonium). Among these counter ions, alkali metal saltsare preferred and a lithium salt is more preferred because thesolubility of dye and the stability of ink are enhanced.

As for the number of ionic hydrophilic groups, the phthalocyanine dyepreferably contains at least two ionic hydrophilic groups, morepreferably at least two sulfo groups and/or carboxyl groups, within onemolecule.

As for the preferred combination of substituents in the compoundrepresented by formula (II), a compound where at least one of varioussubstituents is the preferred group is preferred, a compound where alarger number of various substituents are the preferred groups is morepreferred, and a compound where all substituents are the preferredgroups is most preferred.

As for the chemical structure of the phthalocyanine dye of the presentinvention, at least one electron-withdrawing group such as sulfinylgroup, sulfonyl group and sulfamoyl group is preferably introduced intorespective four benzene rings of phthalocyanine such that the total ofσp values of the substituents in the entire phthalocyanine skeletonbecomes 1.6 or more.

The Hammett's substituent constant σp value is briefly described here.The Hammett's rule is an empirical rule advocated by L. P. Hammett in1935 so as to quantitatively discuss the effect of substituent on thereaction or equilibrium of benzene derivatives and its propriety iswidely admitted at present. The substituent constant determined by theHammett's rule includes a up value and a σm value and these values canbe found in a large number of general publications but these aredescribed in detail, for example, in J. A. Dean (compiler), Lange'sHandbook of Chemistry, 12th ed., McGraw-Hill (1979), and Kagakuno Ryoiki(Chemistry Region), special number, No. 122, pp. 96-103, Nankodo (1979).

Inevitably in view of the synthesis method, the phthalocyaninederivative represented by formula (I) is generally a mixture ofanalogues differing in the site where the substituents Xn (n=1 to 4) andYm (m=1 to 4) are introduced and in the number of the substituentsintroduced. Accordingly, these analogue mixtures are statisticallyaveraged and represented by a formula in many cases. In the presentinvention, it has been found that when these analogue mixtures areclassified into the following three types, a specific mixture isparticularly preferred. The phthalocyanine-base dye analogue mixturesrepresented by formulae (I) and (II) are defined by classifying theseinto the following three types based on the substitution site. Y₁₁, Y₁₂,Y₁₃, Y₁₄, Y₁₅, Y₁₆, Y₁₇ and Y₁₈ in formula (II) are designated as the1-position, 4-position, 5-position, 8-position, 9-position, 12-position,13-position and 16-position, respectively.

(1) β-Position Substitution Type:

A phthalocyanine dye having specific substituents at the 2- and/or3-position, the 6- and/or 7-position, the 10- and/or 11-position, andthe 14- and/or 15-position.

(2) α-Position Substitution Type:

A phthalocyanine dye having specific substituents at the 1- and/or4-position, the 5- and/or 8-position, the 9- and/or 12-position, and the13- and/or 16-position.

(3) α,β-Position Mixed Substitution Type:

A phthalocyanine dye having specific substitutions at the 1- to16-positions without any regularity.

In the present invention, phthalocyanine dye derivatives differing inthe structure (particularly in the substitution site) are described byusing these β-position substitution type, α-position substitution typeand α,β-position mixed substitution type.

The phthalocyanine derivative for use in the present invention can besynthesized by combining the methods described or cited, for example, inShirai and Kobayashi, Phthalocyanine—Kagaku toKino—(Phthalocyanine—Chemistry and Function—), pp. 1-62, IPC, and C. C.Leznoff and A. B. P. Lever, Phthalocyanines—Properties and Applications,pp. 1-54, VCH, or methods analogous thereto.

The phthalocyanine compound represented by formula (I) of the presentinvention can be synthesized, for example, through sulfonation, sulfonylchloridation or amidation reaction of an unsubstituted phthalocyaninecompound as described in International Publications 00/17275, 00/08103,00/08101 and 98/41853 and JP-A-10-36471. In this case, sulfonation maytake place at any site of the phthalocyanine nucleus and the number ofsites sulfonated is difficult to control. Accordingly, when a sulfogroup is introduced under such reaction conditions, the positions andnumber of sulfo groups introduced into the product cannot be specifiedand a mixture of those differing in the number of substituents or in thesubstitution site inevitably results. If the compound of the presentinvention is synthesized starting from such a product, the compound ofthe present invention is obtained as an α,β-position mixed substitutiontype mixture containing several kinds of compounds differing in thenumber of substituents or in the substitution site because the number ofsulfamoyl groups substituted on the heterocyclic ring or theirsubstitution sites cannot be specified.

As described above, for example, when many electron-withdrawing groupssuch as sulfamoyl group are introduced into the phthalocyanine nucleus,the oxidation potential becomes nobler and the ozone resistance isincreased. However, according to the above-described synthesis method, aphthalocyanine dye where the number of electron-withdrawing groupsintroduced is small, namely, the oxidation potential is baser, isinevitably mingled. Therefore, in order to improve the ozone resistance,it is preferred to use a synthesis method where the production of acompound having a baser oxidation potential is suppressed

The phthalocyanine compound represented by formula (II) of the presentinvention can be synthesized, for example, by reacting a phthalonitrilederivative (Compound P) shown below and/or a diiminoisoindolinederivative (Compound Q) shown below with a metal derivative representedby formula (III) or can be derived from a tetrasulfophthalocyaninecompound obtained by reacting a 4-sulfophthalonitrile derivative(Compound R) shown below with a metal derivative represented by formula(III).

In the formulae above, X_(p) corresponds to X₁₁, X₁₂, X₁₃ or X₁₄ informula (II) and Y_(q) and Y_(q′) each corresponds to Y₁₁, Y₁₂, Y₁₃,Y₁₄, Y₁₅, Y₁₆, Y₁₇ or Y₁₈ in formula (II). In Compound R, M′ representscation.

Examples of the cation represented by M′ include alkali metal ions suchas Li, Na and K, and organic cations such as triethylammonium ion andpyridinium ion.M-(Y)_(d)   Formula (III):wherein M has the same meaning as M in formulae (I) and (II), Yrepresents a monovalent or divalent ligand such as halogen atom, acetateanion, acetylacetonate and oxygen, and d represents an integer of 1 to4.

That is, according to this synthesis method, a specific number ofdesired substituents can be introduced. Particularly, in the case ofintroducing a large number of electron-withdrawing groups so as torender the oxidation potential nobler as in the present invention, thissynthesis method is very excellent as compared with the above-describedmethod for synthesizing the phthalocyanine compound of formula (I).

The thus-obtained phthalocyanine compound represented by formulae (II)is usually a mixture of compounds represented by the following formulae(a)-1 to (a)-4 which are isomers with respect to the substitution siteof each X_(p), namely, a β-position substitution type.

In the synthesis method above, when all X_(p)s are the same, aβ-position substitution type phthalocyanine dye where X₁₁, X₁₂, X₁₃ andX₁₄ are completely the same substituents can be obtained. On the otherhand, when X_(p)s are different, a dye having substituents of the samekind but partially different from each other or a dye havingsubstituents different from each other can be synthesized. Among thedyes of formula (II), these dyes having electron-withdrawingsubstituents different from each other are preferred because thesolubility and aggregating property of dye and the aging stability ofink can be controlled.

In the present invention, it has been found very important for theimprovement of fastness that in any substitution type, the oxidationpotential is nobler than 1.0 V (vs SCE). The great effect thereof cannotbe expected at all from the above-described known techniques.Furthermore, although the reason is not particularly known, there is atendency that the β-position substitution type is apparently moreexcellent in the color hue, light fastness, ozone gas resistance and thelike than the α,β-position mixed substitution type.

Specific examples (Compounds I-1 to I-12 and 101 to 190) of thephthalocyanine dyes represented by formulae (I) and (II) are set forthbelow, but the phthalocyanine dye for use in the present invention isnot limited to the following examples.Compounds:

In the following Tables, specific examples of each pair of (X1, X2),(Y11, Y12), (Y13, Y14), (Y15, Y16) and (Y17, Y18) are independently inan irregular order.

Compound No. M X1 X2 Y11,Y12 Y13,Y14 Y15,Y16 Y17,Y18 101 Cu—SO₂—NH—CH₂—CH₂—SO₃Li —H —H, —H —H, —H —H, —H —H, —H 102 Cu

—H —Cl, —H —Cl, —H —Cl, —H —Cl, —H 103 Cu

—H —H, —H —H, —H —H, —H —H, —H 104 Cu

—H —H, —H —H, —H —H, —H —H, —H 105 Ni

—H —Cl, —H —Cl, —H —Cl, —H —Cl, —H 106 Cu—SO₂—NH—CH₂—CH₂—SO₂NH—CH₂—COONa —CN —H, —H —H, —H —H, —H —H, —H 107 Cu

—H —H, —H —H, —H —H, —H —H, —H 108 Cu —SO₂—CH₂—CH₂—CH₂—SO₃Li —H —H, —H—H, —H —H, —H —H, —H 109 Cu —SO₂—CH₂—CH₂—CH₂—SO₃K —H —H, —H —H, —H —H,—H —H, —H 110 Cu —SO₂—(CH₂)₅—CO₂K —H —H, —H —H, —H —H, —H —H, —H 111 Cu

—H —H, —H —H, —H —H, —H —H, —H 112 Cu

—SO₃Li —H, —H —H, —H —H, —H —H, —H 113 Cu

—H —H, —H —H, —H —H, —H —H, —H 114 Cu

—SO₃Li —H, —H —H, —H —H, —H —H, —H 115 Cu

—H —H, —H —H, —H —H, —H —H, —H 116 Cu

—H —H, —H —H, —H —H, —H —H, —H 117 Cu

—H —H, —H —H, —H —H, —H —H, —H 118 Cu

—H —H, —H —H, —H —H, —H —H, —H 119 Cu

—H —H, —H —H, —H —H, —H —H, —H 120 Cu

—H —H, —H —H, —H —H, —H —H, —H 121 Cu

—H —H, —H —H, —H —H, —H —H, —H 122 Cu

—H —H, —H —H, —H —H, —H —H, —H 123 Cu —SO₂NH—C₈H₁₇(t) —H —H, —H —H, —H—H, —H —H, —H 124 Cu

—H —H, —H —H, —H —H, —H —H, —H 125 Cu

—H —H, —H —H, —H —H, —H —H, —H 126 Cu

—H —H, —H —H, —H —H, —H —H, —H 127 Cu

—H —H, —H —H, —H —H, —H —H, —H 128 Zn

—CN —H, —H —H, —H —H, —H —H, —H 129 Cu

—H —Cl, —H —Cl, —H —Cl, —H —Cl, —H 130 Cu

—H —H, —H —H, —H —H, —H —H, —H 131 Cu

—H —H, —H —H, —H —H, —H —H, —H 132 Cu

—H —H, —H —H, —H —H, —H —H, —H 133 Cu

—H —H, —H —H, —H —H, —H —H, —H 134 Cu

—H —H, —H —H, —H —H, —H —H, —H 135 Cu

—H —H, —H —H, —H —H, —H —H, —H 136 Cu

—H —H, —H —H, —H —H, —H —H, —H 137 Cu

—H —H, —H —H, —H —H, —H —H, —H 138 Cu

—H —H, —H —H, —H —H, —H —H, —H 139 Cu

—Cl —H, —H —H, —H —H, —H —H, —H 140 Cu

—H —H, —H —H, —H —H, —H —H, —H 141 Cu

—H —H, —H —H, —H —H, —H —H, —H 14Z Cu

—H —H, —H —H, —H —H, —H —H, —H 143 Cu

—H —H, —H —H, —H —H, —H —H, —H 144 Cu

—H —H, —H —H, —H —H, —H —H, —H 145 Cu —SO₂CH₂CH₂OCH₂CH₂OCH₂CH₂SO₃Li —H,—H, —H —H, —H —H, —H —H, —H

In the following Tables, each introduction site of substituents (X_(p1))and (X_(p2)) is in an irregular order within the β-position substitutiontype. M—Pc(Xp₁)_(m)(Xp₂)_(n) Compound No. M Xp₁ m Xp₁ n 146 Cu

3

1 147 Cu —SO₂—NH—CH₂—CH₂SO₃Li 3

1 148 Cu

3 —SO₂NH—CH₂—CH₂—CH₂—SO₂NH—CH₂CH₂—O—CH₂—CH₂—OH 1 149 Cu

2

2 150 Cu —SO₂—NH—CH₂CH₂SO₂NH—CH₂CH₂—COONa 3

1 151 Cu

3 —SO₂NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 152 Cu

2.5 —SO₂—CH₂—CH₂—O—CH₂—CH₂—OH 1.5 153 Cu

2

2 154 Cu —SO₂—CH₂—CH₂—CH₂—SO₃Li 3

1 155 Cu —SO₂—CH₂—CH₂—CH₂—COOK 2

2 156 Cu —SO₂—CH₂—CH₂—CH₂—SO₃Li 3

1 157 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—SO₃Li 2

2 158 Cu

3

1 159 Cu —SO₂NHCH₂CH₂—SO₃Li 3

1 160 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—SO₃Na 3

1 161 Cu —SO₂CH₂CH₂CH₂SO₃Li 3

1 162 Cu —SO₂CH₂CH₂CH₂SO₃Li 2 —SO₂CH₂CH₂OCH₂CH₂OCH₂CH₂OH 2 163 Cu—SO₂CH₂CH₂CH₂SO₃K 3

1 164 Cu —SO₂CH₂CH₂CH₂SO₃Li 2 —SO₂CH₂CH₂CH₂SO₂N(CH₂CH₂OH)₂ 2 165 Cu—CO—NH—CH₂—CH₂—SO₃K 3 —CO—NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 166 Cu—CO—NH—CH₂—CH₂—SO₂—NH—CH₂—CH₂—COONa 3

1 167 Cu

2.5

1.5 168 Cu

2

2 169 Cu —CO₂—CH₂—CH₂—CH₂—SO₃Li 3

1 170 Cu —CO₂—CH₂—CH₂—CH₂COOK 2

2 171 Cu —CO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—SO₃Na 3

1 172 Cu —SO₂CH₂CH₂OCH₂CH₂O—CH₂CH₂SO₃K 2

2 173 Cu

2

2 174 Cu

3

1 175 Cu —SO₂(CH₂)₃SO₂NH(CH₂)₃N(CH₂CH₂OH)₂ 2

2 176 Cu

3

1 177 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 2

1 178 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—OH 3

1 179 Cu

2

2 180 Cu

3 —SO₂NH—CH₂CH₂—SO₂NH—CH₂CH₂—O—CH₂—CH₂—OH 1 181 Cu

3

1 182 Cu

2.5

1.5 183 Cu

2 —SO₂—CH₂—CH₂—CH₂—SO₂—NH—(CH₂)₃—CH₂—O—CH₂CH₂—OH 2 184 Cu

3 —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1 185 Cu

3 —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1 186 Cu

3 —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—OH 1 187 Cu

3

1 188 Cu

3 —CO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1 189 Cu

3

1 190 Cu

3 —CO—NH—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1

The structure of the phthalocyanine compound represented byM-Pc(X_(p1))_(m)(X_(p2))_(n) in Compound Nos. 146 to 190 is shown below:

(wherein each X_(p1) is independently X_(p1) or X_(p2)).

The phthalocyanine dye represented by formula (I) can be synthesizedaccording to the patent publications described above. Furthermore, thephthalocyanine dye represented by formula (II) can be synthesized by themethods described in JP-A-2001-226275, JP-A-2001-96610, JP-A-2001-47013and JP-A-2001-193638 in addition to the above-described synthesismethod. The starting material, dye intermediate and synthesis route arenot limited to those described in these patent publications.

The inkjet recording ink composition of the present invention (in thepresent invention, this is sometimes simply referred to as the “link”)is obtained by dissolving or dispersing at least one phthalocyanine dyedescribed above in an aqueous medium and preferably contains the dye inan amount of 0.2 to 20 mass %, more preferably from 0.5 to 15 mass %.

In the ink of the present invention, other dyes and pigments may be usedin combination with the above-described azo or phthalocyanine dye so asto constitute an ink set for obtaining a full color image or adjust thecolor tone. Examples of the dye which can be used in combination includethe following dyes.

Examples of the yellow dye include aryl- or heteryl-azo dyes having aphenol, a naphthol, an aniline, a pyrazolone, a pyridone or an openchain-type active methylene compound as the coupling component;azomethine dyes having an open chain-type active methylene compound asthe coupling component; methine dyes such as benzylidene dye andmonomethine oxonol dye; and quinone-base dyes such as naphthoquinone dyeand anthraquinone dye. Other examples of the dye species includequinophthalone dye, nitro·nitroso dye, acridine dye and acridinone dye.These dyes may be a dye which provides a yellow color for the first timewhen a part of the chromophore is dissociated. In this case, the countercation may be an inorganic cation such as alkali metal and ammonium, anorganic cation such as pyridinium and quaternary ammonium salt, or apolymer cation having such a cation in the partial structure.

Examples of the magenta dye include aryl- or heteryl-azo dyes having aphenol, a naphthol or an aniline as the coupling component; azomethinedyes having a pyrazolone or a pyrazolotriazole as the couplingcomponent; methine dyes such as arylidene dye, styryl dye, merocyaninedye and oxonol dye; carbonium dyes such as diphenylmethane dye,triphenylmethane dye and xanthene dye; quinone-base dyes such asnaphthoquinone, anthraquinone and anthrapyridone; and condensedpolycyclic dyes such as dioxazine dye. These dyes may be a dye whichprovides a magenta color for the first time when a part of thechromophore is dissociated. In this case, the counter cation may be aninorganic cation such as alkali metal and ammonium, an organic cationsuch as pyridinium and quaternary ammonium salt, or a polymer cationhaving such a cation in the partial structure.

Examples of the cyan dye include azomethine dyes such as indoaniline dyeand indophenol dye; polymethine dyes such as cyanine dye, oxonol dye andmerocyanine dye; carbonium dyes such as diphenylmethane dye,triphenylmethane dye and xanthene dye; phthalocyanine dyes;anthraquinone dyes; aryl- or heteryl-azo dyes having a phenol, anaphthol or an aniline as the coupling component; and indigo·thioindigodyes. These dyes may be a dye which provides a cyan color for the firsttime when a part of the chromophore is dissociated. In this case, thecounter cation may be an inorganic cation such as alkali metal andammonium, an organic cation such as pyridinium and quaternary ammoniumsalt, or a polymer cation having such a cation in the partial structure.

A black dye such as polyazo dye can also be used.

Examples of the water-soluble dye include direct dye, acid dye, foodcolor, basic dye and reactive dye. Preferred examples thereof includeC.I. Direct Red 2, 4, 9, 23, 26, 31, 39, 62, 63, 72, 75, 76, 79, 80, 81,83, 84, 89, 92, 95, 111, 173, 184, 207, 211, 212, 214, 218, 21, 223,224, 225, 226, 227, 232, 233, 240, 241, 242, 243 and 247; C.I. DirectViolet 7, 9, 47, 48, 51, 66, 90, 93, 94, 95, 98, 100 and 101; C.I.direct Yellow 8, 9, 11, 12, 27, 28, 29, 33, 35, 39, 41, 44, 50, 53, 58,59, 68, 86, 87, 93, 95, 96, 98, 100, 106, 108, 109, 110, 130, 132, 142,144, 161 and 163; C.I. Direct Blue 1, 10, 15, 22, 25, 55, 67, 68, 71,76, 77, 78, 80, 84, 86, 87, 90, 98, 106, 108, 109, 151, 156, 158, 159,160, 168, 189, 192, 193, 194, 199, 200, 201, 202, 203, 207, 211, 213,214, 218, 225, 229, 236, 237, 244, 248, 249, 251, 252, 264, 270, 280,288, 289 and 291; C.I. Direct Black 9, 17, 19, 22, 32, 51, 56, 62, 69,77, 80, 91, 94, 97, 108, 112, 113, 114, 117, 118, 121, 122, 125, 132,146, 154, 166, 168, 173 and 199; C.I. Acid Red 35, 42, 52, 57, 62, 80,82, 111, 114, 118, 119, 127, 128, 131, 143, 151, 154, 158, 249, 254,257, 261, 263, 266, 289, 299, 301, 305, 336, 337, 361, 396 and 397; C.I.Acid Violet 5, 34, 43, 47, 48, 90, 103 and 126; C.I. Acid Yellow 17, 19,23, 25, 39, 40, 42, 44, 49, 50, 61, 64, 76, 79, 110, 127, 135, 143, 151,159, 169, 174, 190, 195, 196, 197, 199, 218, 219, 222 and 227; C.I. AcidBlue 9, 25, 40, 41, 62, 72, 76, 78, 80, 82, 92, 106, 112, 113, 120,127:1, 129, 138, 143, 175, 181, 205, 207, 220, 221, 230, 232, 247, 258,260, 264, 271, 277, 278, 279, 280, 288, 290 and 326; C.I. Acid Black 7,24, 29, 48, 52:1 and 172; C.I. Reactive Red 3, 13, 17, 19, 21, 22, 23,24, 29, 35, 37, 40, 41, 43, 45, 49 and 55; C.I. Reactive Violet 1, 3, 4,5, 6, 7, 8, 9, 16, 17, 22, 23, 24, 26, 27, 33 and 34; C.I. ReactiveYellow 2, 3, 13, 14, 15, 17, 18, 23, 24, 25, 26, 27, 29, 35, 37, 41 and42; C.I. Reactive Blue 2, 3, 5, 8, 10, 13, 14, 15, 17, 18, 19, 21, 25,26, 27, 28, 29 and 38; C.I. Reactive Black 4, 5, 8, 14, 21, 23, 26, 31,32 and 34; C.I. Basic Red 12, 13, 14, 15, 18, 22, 23, 24, 25, 27, 29,35, 36, 38, 39, 45 and 46; C.I. Basic Violet 1, 2, 3, 7, 10, 15, 16, 20,21, 25, 27, 28, 35, 37, 39, 40 and 48; C.I. Basic Yellow 1, 2, 4, 11,13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 39 and 40; C.I. BasicBlue 1, 3, 5, 7, 9, 22, 26, 41, 45, 46, 47, 54, 57, 60, 62, 65, 66, 69and 71; and C.I. Basic Black 8.

As the pigment (including those called a dye) for use in the presentinvention, commercially available pigments and known pigments describedin various publications can be used. The publication includes ColorIndex, compiled by The Society of Dyers and Colourists, Kaitei Shin HanGanryo Binran (Revised New Handbook of Pigments), compiled by NipponGanryo Gijutsu Kyokai (1989), Saishin Ganryo Oyo Gijutsu (Newest PigmentApplication Technology), CMC Shuppan (1986), Insatsu Ink Gijutsu(Printing Ink Technique), CMC Shuppan (1984), and W. Herbst and K.Hunger, Industrial Organic Pigments, VCH Verlagsgesellschaft (1993).Specific examples of the organic pigment include azo pigments (e.g., azolake pigment, insoluble azo pigment, condensed azo pigment, chelate azopigment), polycyclic pigments (e.g., phthalocyanine-base pigment,anthraquinone-base pigment, perylene-base and perynone-base pigment,indigo-base pigment, quinacridone-base pigment, dioxazine-base pigment,isoindolinone-base pigment, quinophthalone-base pigment,diketopyrrolopyrrole-base pigment), dyeing lake pigments (lake pigmentsof acid or basic dye) and azine pigments. Specific examples of theinorganic pigment include yellow pigments such as C.I. Pigment Yellow34, 37, 42 and 53, red-type pigments such as C.I. Pigment Red 101 and108, blue-type pigments such as C.I. Pigment Blue 27, 29 and 17:1,black-type pigments such as C.I. Pigment Black 7 and magnetite, andwhite-type pigments such as C.I. Pigment White 4, 6, 18 and 21.

The pigments having a preferred color tone for the formation of an imageinclude the followings. As the blue to cyan pigment, phthalocyaninepigments, anthraquinone-base indanthrone pigments (for example, C.I.Pigment Blue 60) and dyeing lake pigment-type triarylcarbonium pigmentsare preferred, and phthalocyanine pigments are most preferred (preferredexamples thereof include copper phthalocyanine such as C.I. Pigment Blue15:1, 15:2, 15:3, 15:4 and 15:6, monochloro or low chlorinatedphthalocyanine, aluminum phthalocyanine such as pigments described inEuropean Patent 860475, nonmetallic phthalocyanine such as C.I. PigmentBlue 16, and phthalocyanine with the center metal being Zn, Ni or Ti,and among these, C.I. Pigment Blue 15:3 and 15:4 and aluminumphthalocyanine are more preferred).

As the red to violet pigment, azo pigments (preferred examples thereofinclude C.I. Pigment Red 3, 5, 11, 22, 38, 48:1, 48:2, 48:3, 48:4, 49:1,52:1, 53:1, 57:1, 63:2, 144, 146 and 184, and among these, C.I. PigmentRed 57:1, 146 and 184 are more preferred), quinacridone-base pigments(preferred examples thereof include C.I. Pigment Red 122, 192, 202, 207and 209 and C.I. Pigment Violet 19 and 42, and among these, C.I. PigmentRed 122 is more preferred), dyeing lake pigment-type triarylcarboniumpigments (preferred examples thereof include xanthene-base C.I. PigmentRed 81:1 and C.I. Pigment Violet 1, 2, 3, 27 and 39), dioxazine-basepigments (for example, C.I. Pigment Violet 23 and 37),diketopyrrolopyrrole-base pigments (for example, C.I. Pigment Red 254),perylene pigments (for example, C.I. Pigment Violet 29),anthraquinone-base pigments (for example, C.I. Pigment Violet 5:1, 31and 33) and thioindigo-base pigments (for example, C.I. Pigment Red 38and 88) are preferred.

As the yellow pigment, azo pigments (preferred examples thereof includemonoazo pigment-type C.I. Pigment Yellow 1, 3, 74 and 98, disazopigment-type C.I. Pigment Yellow 12, 13, 14, 16, 17 and 83, syntheticazo-type C.I. Pigment 93, 94, 95, 128 and 155, and benzimidazolone-typeC.I. Pigment Yellow 120, 151, 154, 156 and 180, and among these, thosenot using a benzidine-base compound as a raw material are morepreferred), isoindoline·isoindolinone-base pigments (preferred examplesthereof include C.I. Pigment Yellow 109, 110, 137 and 139,),quinophthalone pigments (preferred examples thereof include C.I. PigmentYellow 138) and flavanthrone pigments (for example, C.I. Pigment Yellow24) are preferred.

As the black pigment, inorganic pigments (preferred examples thereofinclude carbon black and magnetite) and aniline black are preferred.

Other than these, an orange pigment (for example, C.I. Pigment Orange 13and 16) and a green pigment (for example, C.I. Pigment Green 7) may beused.

The above-described pigment which can be used in the present inventionmay be used as it is or may be subjected to a surface treatment. For thesurface treatment, a method of coating the surface with resin or wax, amethod of attaching a surfactant, and a method of binding a reactivesubstance (for example, a radical generated from a silane couplingagent, an epoxy compound, a polyisocyanate or a diazonium salt) to thepigment surface may be used and these are described in the followingpublications and patents:

-   -   (1) Kinzoku Sekken no Seishitsu to Oyo (Properties and        Applications of Metal Soap), Saiwai Shobo;    -   (2) Insatsu Ink Insatsu (Printing Ink Printing), CMC Shuppan        (1984);    -   (3) Saishin Ganryo Oyo Gijutsu (Newest Pigment Application        Technology), CMC Shuppan (1986);    -   (4) U.S. Pat. Nos. 5,554,739 and 5,571,311; and    -   (5) JP-A-9-151342, JP-A-10-140065, JP-A-10-292143 and        JP-A-11-166145.

Particularly, self-dispersible pigments prepared by allowing a diazoniumsalt to act on carbon black described in U.S. Patents of (4) andcapsulated pigments prepared by the method described in Japanese patentpublications of (5) are effective, because dispersion stability can beobtained without using an excess dispersant in the ink.

In the present invention, the pigment may be dispersed by further usinga dispersant. Various known dispersants can be used according to thepigment used, for example, a surfactant-type low molecular dispersant ora polymer-type dispersant can be used. Examples of the dispersantinclude those described in JP-A-3-69949 and European Patent 549486. Inusing the dispersant, a pigment derivative called synergist may also beadded so as to accelerate the adsorption of dispersant to the pigment.

The particle size of the pigment which can be used in the presentinvention is, after the dispersion, preferably from 0.01 to 10 μm, morepreferably from 0.05 to 1 μm.

As for the method of dispersing the pigment, known dispersion techniquesused at the production of ink or toner can be used. Examples of thedispersing machine include vertical or horizontal agitator mill,attritor, colloid mill, ball mill, three-roll mill, pearl mill,super-mill, impeller, disperser, KD mill, dynatron and pressure kneader.These are described in detail in Saishin Ganryo Oyo Gijutsu (NewestPigment Application Technology), CMC Shuppan (1986).

The dye for use in the present invention is substantially water-solubleor water-dispersible. A water-soluble dye preferably having a solubilityof 2 mass % or more, more preferably 5 mass % or more, in water at 20°C. is used.

The ink of the present invention preferably has a conductivity of 0.01to 10 S/m, more preferably from 0.05 to 5 S/m.

The conductivity can be measured by an electrode method using acommercially available saturated potassium chloride.

The conductivity can be controlled mainly by the ion concentration inthe aqueous solution. In the case where the salt concentration is high,desalting may be performed by using an ultrafiltration membrane. Also,in the case of adjusting the conductivity by adding a salt or the like,the conductivity can be adjusted by adding various organic or inorganicsalts.

Examples of the inorganic salt which can be used include inorganiccompounds such as potassium halide, sodium halide, sodium sulfate,potassium sulfate, sodium hydrogensulfate, potassium hydrogensulfate,sodium nitrate, potassium nitrate, sodium hydrogencarbonate, potassiumhydrogen carbonate, sodium phosphate, sodium monohydrogen-phosphate,boric acid, potassium dihydrogenphosphate and sodiumdihydrogenphosphate. Examples of the organic salt which can be usedinclude organic compounds such as sodium acetate, potassium acetate,potassium tartrate, sodium tartrate, sodium benzoate, potassiumbenzoate, sodium p-toluenesulfonate, potassium saccharinate, potassiumphthalate and sodium picolinate.

The conductivity can also be adjusted by selecting the components of theaqueous medium which is described later.

The inkjet recording ink composition of the present invention can beprepared by dissolving and/or dispersing the above-described dye and thebetaine-type surfactant of the present invention in an aqueous medium.The term “aqueous medium” as used in the present invention means wateror a mixture of water and a slight amount of water-miscible organicsolvent, where additives such as surfactant, wetting agent, stabilizerand antiseptic are added, if desired.

The ink composition of the present invention is characterized by havinga betaine-type surfactant in the ink composition. Here, the betaine-typesurfactant includes a surfactant used, for example, for the dispersionof an oily dye.

The betaine-type surfactant as used herein means a compound having botha cationic moiety and an anionic moiety in its molecule and havingsurface activity. Examples of the cationic moiety include an aminicnitrogen atom, a nitrogen atom of heteroaromatic ring, a boron atomhaving 4 bonds to carbon, and a phosphoric atom. Among these, preferredare an aminic nitrogen atom and a nitrogen atom of heteroaromatic ring(preferably imidazole), more preferred is a quaternary nitrogen atom.Examples of the anionic moiety include a hydroxyl group, a thio group, asulfonamide group, a sulfo group, a carboxyl group, an imido group, aphosphoric acid group and a phosphonic acid group. Among these,preferred are a carboxyl group and a sulfo group. The electric charge ofthe surfactant molecule as a whole may be cationic, anionic or neutralbut is preferably neutral.

The betaine-type surfactant is the compound A or B described above,preferably a compound represented by formula (A) or (B).

In formula (B), R_(s4), R_(s5) and R_(s6) each independently representsan alkyl group, an aryl group or a heterocyclic group and may combinewith each other to form a ring structure. R_(s4), R_(s5) and R_(s6) eachindependently represents an alkyl group (which may be substituted;preferably having from 1 to 20 carbon atoms, more preferably from 1 to16 carbon atoms, e.g., methyl, ethyl, propyl, butyl, hexyl, octyl,dodecyl, cetyl, stearyl, oleyl), an aryl group (which may besubstituted; preferably having from 6 to 20 carbon atoms, morepreferably from 6 to 14 carbon atoms, e.g., phenyl, tolyl, xylyl,naphthyl, cumyl, dodecylphenyl) or a heterocyclic group (which may besubstituted; preferably having from 2 to 20 carbon atoms, morepreferably from 2 to 12 carbon atoms, e.g., pyridyl, quinolyl), and maycombine with each other to form a ring structure. Specific examples ofthe ring structure include a piperidine ring and a morpholine ring.R_(s4), R_(s5) and R_(s6) each is preferably an alkyl group.

R_(s7) represents a carboxyl or sulfo group-containing substituent(preferably a carboxyl or sulfo group-containing alkyl, aryl orheterocyclic group). Examples of the alkyl group, aryl group andheterocyclic group are the same as those described above for R_(s4),R_(s5) and R_(s6), and preferred examples are also the same. R_(s7) ispreferably a group represented by -L-COO⁻. L represents a divalentlinking group. Preferred examples thereof include a divalent linkinggroup containing an alkylene group or an arylene group as a fundamentalconstitution unit. In the linking main chain part, a heteroatom such asoxygen atom, sulfur atom and nitrogen atom may be contained. L ispreferably an alkylene group (preferably methylene or ethylene, morepreferably methylene).

R_(s4), R_(s5), R_(s6) and L each may be substituted by varioussubstituents. Examples of the substituent include an alkyl group(preferably having from 1 to 20 carbon atoms, more preferably from 1 to12 carbon atoms, still more preferably from 1 to 8 carbon atoms, e.g.,methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl,cyclopropyl, cyclopentyl, cyclohexyl), an alkenyl group (preferablyhaving from 2 to 20 carbon atoms, more preferably from 2 to 12 carbonatoms, still more preferably from 2 to 8 carbon atoms, e.g., vinyl,allyl, 2-butenyl, 3-pentenyl), an alkynyl group (preferably having from2 to 20 carbon atoms, more preferably from 2 to 12 carbon atoms, stillmore preferably from 2 to 8 carbon atoms, e.g., propargyl, 3-pentynyl),an aryl group (preferably having from 6 to 30 carbon atoms, morepreferably from 6 to 20 carbon atoms, still more preferably from 6 to 12carbon atoms, e.g., phenyl, p-methylphenyl, naphthyl), an amino group(preferably having from 0 to 20 carbon atoms, more preferably from 0 to12 carbon atoms, still more preferably from 0 to 6 carbon atoms, e.g.,amino, methylamino, dimethylamino, diethylamino, diphenylamino,dibenzylamino), an alkoxy group (preferably having from 1 to 20 carbonatoms, more preferably from 1 to 12 carbon atoms, still more preferablyfrom 1 to 8 carbon atoms, e.g., methoxy, ethoxy, butoxy), an aryloxygroup (preferably having from 6 to 20 carbon atoms, more preferably from6 to 16 carbon atoms, still more preferably from 6 to 12 carbon atoms,e.g., phenyloxy, 2-naphthyloxy), an acyl group (preferably having from 1to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, stillmore preferably from 1 to 12 carbon atoms, e.g., acetyl, benzoyl,formyl, pivaloyl), an alkoxycarbonyl group (preferably having from 2 to20 carbon atoms, more preferably from 2 to 16 carbon atoms, still morepreferably from 2 to 12 carbon atoms, e.g., methoxycarbonyl,ethoxycarbonyl), an aryloxycarbonyl group (preferably having from 7 to20 carbon atoms, more preferably from 7 to 16 carbon atoms, still morepreferably from 7 to 10 carbon atoms, e.g., phenyloxycarbonyl), anacyloxy group (preferably having from 2 to 20 carbon atoms, morepreferably from 2 to 16 carbon atoms, still more preferably from 2 to 10carbon atoms, e.g., acetoxy, benzoyloxy), an acylamino group (preferablyhaving from 2 to 20 carbon atoms, more preferably from 2 to 16 carbonatoms, still more preferably from 2 to 10 carbon atoms, e.g.,acetylamino, benzoylamino), an alkoxycarbonylamino group (preferablyhaving from 2 to 20 carbon atoms, more preferably from 2 to 16 carbonatoms, still more preferably from 2 to 12 carbon atoms, e.g.,methoxycarbonylamino), an aryloxycarbonylamino group (preferably havingfrom 7 to 20 carbon atoms, more preferably from 7 to 16 carbon atoms,still more preferably from 7 to 12 carbon atoms, e.g.,phenyloxycarbonylamino), a sulfonylamino group (preferably having from 1to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, stillmore preferably from 1 to 12 carbon atoms, e.g., methanesulfonylamino,benzenesulfonylamino), a sulfamoyl group (preferably having from 0 to 20carbon atoms, more preferably from 0 to 16 carbon atoms, still morepreferably from 0 to 12 carbon atoms, e.g., sulfamoyl, methylsulfamoyl,dimethylsulfamoyl, phenylsulfamoyl), a carbamoyl group (preferablyhaving from 1 to 20 carbon atoms, more preferably from 1 to 16 carbonatoms, still more preferably from 1 to 12 carbon atoms, e.g., carbamoyl,methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl), an alkylthio group(preferably having from 1 to 20 carbon atoms, more preferably from 1 to16 carbon atoms, still more preferably from 1 to 12 carbon atoms, e.g.,methylthio, ethylthio), an arylthio group (preferably having from 6 to20 carbon atoms, more preferably from 6 to 16 carbon atoms, still morepreferably from 6 to 12 carbon atoms, e.g., phenylthio), a sulfonylgroup (preferably having from 1 to 20 carbon atoms, more preferably from1 to 16 carbon atoms, still more preferably from 1 to 12 carbon atoms,e.g., mesyl, tosyl), a sulfinyl group (preferably having from 1 to 20carbon atoms, more preferably from 1 to 16 carbon atoms, still morepreferably from 1 to 12 carbon atoms, e.g., methanesulfinyl,benzenesulfinyl), a ureido group (preferably having from 1 to 20 carbonatoms, more preferably from 1 to 16 carbon atoms, still more preferablyfrom 1 to 12 carbon atoms, e.g., ureido, methylureido, phenylureido), aphosphoric acid amide group (preferably having from 1 to 20 carbonatoms, more preferably from 1 to 16 carbon atoms, still more preferablyfrom 1 to 12 carbon atoms, e.g., diethylphosphoric acid amide,phenylphosphoric acid amide), a hydroxy group, a mercapto group, ahalogen atom (e.g., fluorine, chlorine, bromine, iodine), a cyano group,a sulfo group, a carboxyl group, a nitro group, a hydroxamic acid group,a sulfino group, a hydrazino group, an imino group, a heterocyclic group(preferably having from 1 to 30 carbon atoms, more preferably from 1 to12 carbon atoms, and containing, for example, a nitrogen atom, an oxygenatom or a sulfur atom as the heteroatom, e.g., imidazolyl, pyridyl,quinolyl, furyl, thienyl, piperidyl, morpholino, benzoxazolyl,benzimidazolyl, benzothiazolyl, carbazolyl, azepinyl) and a silyl group(preferably having from 3 to 40 carbon atoms, more preferably from 3 to30 carbon atoms, still more preferably from 3 to 24 carbon atoms, e.g.,trimethylsilyl, triphenylsilyl). These substituents each may be furthersubstituted. When two or more substituents are present, these may be thesame or different and if possible, these substituents may combine witheach other to form a ring. Also, a plurality of betaine structures maybe contained through R_(s4), R_(s5), R_(s6) or L.

In the compound represented by formula (B) of the present invention, thecase where at least one of the groups represented by R_(s4), R_(s5),R_(s6) and L contains a group having 8 or more carbon atoms ispreferred, the case where R_(s4), R_(s5) or R_(s6) contains a long-chainalkyl group is more preferred, and the case where L representsCH(R_(s8)), R_(s8) represents a hydrogen atom or an alkyl group having 8or more carbon atoms and any one of R_(s4), R_(s5), R_(s6) and R_(s8) isan alkyl group having 8 or more carbon atoms is still more preferred.

In the compound represented by formula (A) of the present invention,R_(s1) and R_(s2) each independently represents an alkyl group andR_(s3) represents a carboxy or sulfo group-containing alkyl group.

Examples of the alkyl group represented by R_(s1) and R_(s2) are thesame as those described above for R_(s4), R_(s5) and R_(s6).

Examples of R_(s3) are the same as those of R_(s7). R_(s7) is preferablya carboxylalkyl or sulfoalkyl group (the number of carbon atoms in thealkyl moiety of the group is preferably from 1 to 6, more preferablyfrom 1 to 4).

The preferred amount of the betaine-type surfactant added (including theamount of the betaine-type surfactant used for the dispersion of dye)extends over a wide range, but the amount added is preferably from 0.001to 50 mass %, more preferably from 0.01 to 20 mass %, even morepreferably from 0.01 to 15 mass %, still more preferably from 0.01 to 10mass %, yet still more preferably from 0.01 to 5 mass %, in the inkcomposition.

Specific examples of the betaine-type surfactant are set forth below,but the present invention is of course not limited thereto.

Other than the surfactant of the present invention, a differentsurfactant can be used in combination. In this case, a nonionicsurfactant is preferred.

Examples of the nonionic surfactant include polyoxyethylene nonylphenylether, polyoxyethylene naphthyl ether and polyoxyethylene octylphenylether.

The nonionic surfactant content is from 0.001 to 15 mass %, preferablyfrom 0.005 to 10 mass %, more preferably from 0.01 to 5 mass %, based onthe ink.

Examples of the water-miscible organic solvent which can be used in thepresent invention include alcohols (e.g., methanol, ethanol, propanol,isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, pentanol,hexanol, cyclohexanol, benzyl alcohol), polyhydric alcohols (e.g.,ethylene glycol, diethylene glycol, triethylene glycol, polyethyleneglycol, propylene glycol, dipropylene glycol, polypropylene glycol,butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol,thiodiglycol), glycol derivatives (e.g., ethylene glycol monomethylether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether,diethylene glycol monomethyl ether, diethylene glycol monobutyl ether,propylene glycol monomethyl ether, propylene glycol monobutyl ether,dipropylene glycol monomethyl ether, triethylene glycol monomethylether, ethylene glycol diacetate, ethylene glycol monomethyl etheracetate, triethylene glycol monomethyl ether, triethylene glycolmonoethyl ether, ethylene glycol monophenyl ether), amines (e.g.,ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine,N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine,diethylenetriamine, triethylenetetramine, polyethyleneimine,tetramethyl-propylenediamine) and other polar solvents (e.g., formamide,N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide,sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone,2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone).These water-miscible organic solvents can be used in combination of twoor more thereof.

In preparing the ink composition of the present invention, in the caseof a water-soluble ink, the dye and the surfactant are preferably firstdissolved in water and thereafter, various solvents and additives areadded, dissolved and mixed to provide a uniform ink solution.

For dissolving the dye and the like, various methods such as stirring,ultrasonic irradiation and shaking can be used. Among these, stirring ispreferred. In performing the stirring, various systems known in thisfield can be used, such as flow stirring and stirring utilizing theshearing force by means of a reversal agitator or a dissolver. Also, astirring method utilizing the shearing force with the bottom surface ofa container, such as magnetic stirrer, can be advantageously used.

In the case where the dye is an oil-soluble dye, the ink composition canbe prepared by dissolving the oil-soluble dye in a high boiling pointorganic solvent and emulsion-dispersing it in an aqueous medium.

The high boiling point organic solvent for use in the present inventionhas a boiling point of 150° C. or more, preferably 170° C. or more.

Examples of the high boiling point organic solvent include phthalic acidesters (e.g., dibutyl phthalate, dioctyl phthalate, dicyclohexylphthalate, di-2-ethylhexyl phthalate, decyl phthalate,bis(2,4-di-tert-amylphenyl) isophthalate, bis(1,1-diethylpropyl)phthalate), esters of phosphoric acid or phosphone (e.g., diphenylphosphate, triphenyl phosphate, tricresyl phosphate,2-ethylhexyldiphenyl phosphate, dioctylbutyl phosphate, tricyclohexylphosphate, tri-2-ethylhexyl phosphate, tridodecyl phosphate,di-2-ethylhexylphenyl phosphate), benzoic acid esters (e.g.,2-ethylhexyl benzoate, 2,4-dichlorobenzoate, dodecyl benzoate,2-ethylhexyl-p-hydroxybenzoate), amides (e.g., N,N-diethyldodecanamide,N,N-diethyllaurylamide), alcohols or phenols (e.g., isostearyl alcohol,2,4-di-tert-amylphenol), aliphatic esters (e.g., dibutoxyethylsuccinate, di-2-ethylhexyl succinate, 2-hexyldecyl tetradecanoate,tributyl citrate, diethyl azelate, isostearyl lactate, trioctylcitrate), aniline derivatives (e.g.,N,N-dibutyl-2-butoxy-5-tert-octylaniline), chlorinated paraffins (e.g.,paraffins having a chlorine content of 10 to 80%), trimesic acid esters(e.g., tributyl trimesate), dodecylbenzene, diisopropylnaphthalene,phenols (e.g., 2,4-di-tert-amylphenol, 4-dodecyloxyphenol,4-dodecyloxycarbonylphenol, 4-(4-dodecyloxyphenylsulfonyl)phenol),carboxylic acids (e.g., 2-(2,4-di-tert-amylphenoxy)butyric acid,2-ethoxyoctane-decanoic acid) and alkylphosphoric acids (e.g.,di-(2-ethylhexyl)phosphoric acid and diphenylphosphoric acid). The highboiling point organic solvent can be used in an amount of, in terms ofmass ratio to the oil-soluble dye, from 0.01 to 3 times, preferably from0.01 to 1.0 times.

These high boiling point organic solvents may be used individually or asa mixture of several kinds [for example, tricresyl phosphate and dibutylphthalate, trioctyl phosphate and di(2-ethylhexyl) sebacate, or dibutylphthalate and poly(N-tert-butylacrylamide)].

Examples of the high boiling point organic solvent for use in thepresent invention, other than the above-described compounds, and/or thesynthesis method of these high boiling point organic solvents aredescribed in U.S. Pat. Nos. 2,322,027, 2,533,514, 2,772,163, 2,835,579,3,594,171, 3,676,137, 3,689,271, 3,700,454, 3,748,141, 3,764,336,3,765,897, 3,912,515, 3,936,303, 4,004,928, 4,080,209, 4,127,413,4,193,802, 4,207,393, 4,220,711, 4,239,851, 4,278,757, 4,353,979,4,363,873, 4,430,421, 4,430,422, 4,464,464, 4,483,918, 4,540,657,4,684,606, 4,728,599, 4,745,049, 4,935,321 and 5,013,639, EP-A-276319,EP-A-286253, EP-A-289820, EP-A-309158, EP-A-309159, EP-A-309160,EP-A-509311, EP-A-510576, East German Patents 147,009, 157,147, 159,573and 225,240A, British Patent 2091124A, JP-A-48-47335, JP-A-50-26530,JP-A-51-25133, JP-A-51-26036, JP-A-51-27921, JP-A-51-27922,JP-A-51-149028, JP-A-52-46816, JP-A-53-1520, JP-A-53-1521,JP-A-53-15127, JP-A-53-146622, JP-A-54-91325, JP-A-54-106228,JP-A-54-118246, JP-A-55-59464, JP-A-56-64333, JP-A-56-81836,JP-A-59-204041, JP-A-61-84641, JP-A-62-118345, JP-A-62-247364,JP-A-63-167357, JP-A-63-214744, JP-A-63-301941, JP-A-64-9452,JP-A-64-9454, JP-A-64-68745, JP-A-1-101543, JP-A-1-102454, JP-A-2-792,JP-A-2-4239, JP-A-2-43541, JP-A-4-29237, JP-A-4-30165, JP-A-4-232946 andJP-A-4-346338.

The high boiling point organic solvent is used in an amount of, in termsof mass ratio to the oil-soluble dye, from 0.01 to 3 times, preferablyfrom 0.01 to 1.0 times.

In the present invention, the oil-soluble dye or high boiling pointorganic solvent is used by emulsion-dispersing it in an aqueous medium.Depending on the case, a low boiling point organic solvent may be usedin combination at the emulsion-dispersion in view of emulsifiability.The low boiling point organic solvent is an organic solvent having aboiling point of about 30 to 150° C. under atmospheric pressure.Preferred examples thereof include, but are not limited to, esters(e.g., ethyl acetate, butyl acetate, ethyl propionate, β-ethoxyethylacetate, methylcellosolve acetate), alcohols (e.g., isopropyl alcohol,n-butyl alcohol, secondary butyl alcohol), ketones (e.g., methylisobutyl ketone, methyl ethyl ketone, cyclohexanone), amides (e.g.,dimethylformamide, N-methylpyrrolidone) and ethers (e.g.,tetrahydrofuran, dioxane).

In the emulsion-dispersion, an oil phase obtained by dissolving the dyein a high boiling organic solvent or depending on the case, in a mixedsolvent of a high boiling organic solvent and a low boiling organicsolvent is dispersed in an aqueous phase mainly comprising water to formfine oil droplets of the oil phase. At this time, in either one or bothof the aqueous phase and the oil phase, additives described later, suchas surfactant, wetting agent, dye stabilizer, emulsification stabilizer,antiseptic and fungicide, can be added, if desired.

In the general emulsification method, an oil phase is added to anaqueous phase, however, a so-called phase inversion emulsificationmethod of adding dropwise an aqueous phase in an oil phase can also bepreferably used. This emulsification method can also be applied when thedye for use in the present invention is water-soluble and the additiveis oil-soluble.

In performing the emulsion-dispersion, various surfactants can be used.Preferred examples thereof include anionic surfactants such as fattyacid salt, alkylsulfuric ester salt, alkylbenzenesulfonate,alkylnaphthalenesulfonate, dialkylsulfosuccinate, alkyl-phosphoric estersalt, naphthalenesulfonic acid formalin condensate and polyoxyethylenealkylsulfuric ester salt, and nonionic surfactants such aspolyoxyethylene alkyl ether, polyoxyethylene alkylallyl ether,polyoxyethylene fatty acid ester, sorbitan fatty acid ester,polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylamine,glycerin fatty acid ester and oxyethylene oxypropylene block copolymer.Also, SURFYNOLS (produced by Air Products & Chemicals), which are anacetylene-base polyoxyethylene oxide surfactant, are preferably used.Furthermore, amine oxide-type amphoteric surfactants such asN,N-dimethyl-N-alkylamine oxide are preferred. In addition, surfactantsdescribed in JP-A-59-157636 (pages (37) to (38)) and ResearchDisclosure, No. 308119 (1989) can also be used.

For the purpose of stabilizing the dispersion immediately afteremulsification, a water-soluble polymer may be added in combination withthe above-described surfactant. Preferred examples of the water-solublepolymer include polyvinyl alcohol, polyvinylpyrrolidone, polyethyleneoxide, polyacrylic acid, polyacrylamide and copolymers thereof. Otherthan these, natural water-soluble polymers such as polysaccharides,casein and gelatin are also preferably used. Furthermore, for thepurpose of stabilizing the dye dispersion, a polymer which does notsubstantially dissolve in an aqueous medium, such as polyvinyl,polyurethane, polyester, polyamide, polyurea and polycarbonate obtainedby the polymerization of acrylic acid esters, methacrylic acid esters,vinyl esters, acrylamides, methacrylamides, olefins, styrenes, vinylethers or acrylonitriles, can also be used in combination. This polymerpreferably contains —SO₃ ⁻ or —COO⁻. In the case of using this polymerwhich does not substantially dissolve in an aqueous medium, the polymeris preferably used in an amount of 20 mass % or less, more preferably 10mass % or less, based on the high boiling point organic solvent.

In preparing an aqueous ink by dispersing the oil-soluble dye or highboiling point organic solvent according to emulsion-dispersion, thecontrol of particle size is important. In order to elevate the colorpurity or density of an image formed by the inkjet recording, it isessential to reduce the average particle size. The average particle sizeis, in terms of volume average particle size, preferably 1 μm or less,more preferably from 5 to 100 nm.

The volume average particle size and particle size distribution of thedispersed particles can be easily measured by a known method such asstatic light scattering method, dynamic light scattering method,centrifugal precipitation method and the method described in JikkenKagaku Koza (Lecture of Experimental Chemistry), 4th ed., pp. 417-418.For example, the ink is diluted with distilled water to have a particleconcentration of 0.1 to 1 mass %, then, the particle size can be easilymeasured by a commercially available volume average particle sizemeasuring apparatus (for example, Microtrac UPA (manufactured by NikkisoK.K.)). The dynamic light scattering method utilizing the laser Dopplereffect is particularly preferred because even a small particle size canbe measured.

The volume average particle size is an average particle size weightedwith the particle volume and is obtained by multiplying the diameter ofindividual particles in the gathering of particles by the volume of theparticle and dividing the sum total of the obtained values by the totalvolume of the particles. The volume average particle size is describedin Soichi Muroi, Kobunshi Latex no Kagaku (Chemistry of Polymer Latex),page 119, Kobunshi Kanko Kai.

Also, it is revealed that the presence of coarse particles greatlyaffects the printing performance. More specifically, the coarse particleclogs the nozzle of head or even if the nozzle is not clogged, forms asoil to bring about ejection failure or ejection slippage of ink andthis seriously affects the printing performance. In order to preventthese troubles, it is important to reduce the number of particles havinga particle size of 5 μm or more to 10 or less and the number ofparticles having a particle size of 1 μm or more to 1,000 or less, in 1μl of ink prepared.

For removing these coarse particles, a known method such as centrifugalseparation or microfiltration can be used. This separation step may beperformed immediately after the emulsion-dispersion or may be performedimmediately before filling the ink in an ink cartridge after variousadditives such as wetting agent and surfactant are added to theemulsified dispersion.

A mechanically emulsifying apparatus is effective for reducing theaverage particle size and eliminating coarse particles.

As for the emulsifying apparatus, known apparatuses such as simplestirrer, impeller stirring system, in-line stirring system, mill system(e.g., colloid mill) and ultrasonic system can be used, but ahigh-pressure homogenizer is particularly preferred.

The mechanism of the high-pressure homogenizer is described in detail inU.S. Pat. No. 4,533,254 and JP-A-6-47264. Examples of the commerciallyavailable apparatus include Gaulin Homogenizer (manufactured by A.P.VGaulin Inc.), Microfluidizer (manufactured by Microfluidex Inc.) andAltimizer (produced by Sugino Machine).

The high-pressure homogenizer with a mechanism of pulverizing particlesin an ultrahigh pressure jet stream recently described in U.S. Pat. No.5,720,551 is particularly effective for the emulsion-dispersion of thepresent invention. Examples of the emulsifying apparatus using thisultrahigh pressure jet stream include DeBEE2000 (manufactured by BEEInternational Ltd.).

In performing the emulsification by a high-pressure emulsion-dispersingapparatus, the pressure is 50 MPa or more, preferably 60 MPa or more,more preferably 180 MPa or more.

A method of using two or more emulsifying apparatuses, for example, byperforming the emulsification in a stirring emulsifier and then passingthe emulsified product through a high-pressure homogenizer isparticularly preferred. In addition, a method of once performing theemulsion-dispersion by such an emulsifying apparatus and after addingadditives such as wetting agent and surfactant, again passing thedispersion through a high-pressure homogenizer during filling of the inkinto a cartridge is also preferred.

In the case of containing a low boiling point organic solvent inaddition to the high boiling point organic solvent, the low boilingpoint solvent is preferably removed in view of stability of theemulsified product, safety and hygiene. For removing the low boilingpoint solvent, various known methods can be used according to the kindof the solvent, such as evaporation, vacuum evaporation andultrafiltration. This removal of the low boiling point organic solventis preferably performed as soon as possible immediately after theemulsification.

In the inkjet recording ink composition obtained by the presentinvention, additives such as drying inhibitor for preventing cloggingdue to drying of ink at the ejection port, penetration accelerator formore successfully penetrating the ink into paper, ultraviolet absorbent,antioxidant, viscosity adjusting agent, surface tension adjusting agent,dispersant, dispersion stabilizer, fungicide, rust inhibitor, pHadjusting agent, defoaming agent and chelating agent, may beappropriately selected and used in an appropriate amount.

The drying inhibitor for use in the present invention is preferably awater-soluble organic solvent having a vapor pressure lower than water.Specific examples thereof include polyhydric alcohols as represented byethylene glycol, propylene glycol, diethylene glycol, polyethyleneglycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propanediol,1,2,6-hexanetriol, acetylene glycol derivative, glycerin andtrimethylolpropane; lower alkyl ethers of polyhydric alcohol, such asethylene glycol monomethyl(or ethyl) ether, diethylene glycolmonomethyl(or ethyl) ether and triethylene glycol monoethyl(or butyl)ether; heterocyclic rings such as 2-pyrrolidone, N-methyl-2-pyrrolidone,1,3-dimethyl-2-imidazolidinone and N-ethylmorpholine; sulfur-containingcompounds such as sulfolane, dimethylsulfoxide and 3-sulfolene;polyfunctional compounds such as diacetone alcohol and diethanolamine;and urea derivatives. Among these, polyhydric alcohols such as glycerinand diethylene glycol are preferred. These drying inhibitors may be usedindividually or in combination of two or more thereof. In the ink, thedrying inhibitor is preferably contained in an amount of 10 to 50 mass%.

Examples of the penetration accelerator which can be used in the presentinvention include alcohols such as ethanol, isopropanol, butanol,di(tri)ethylene glycol monobutyl ether and 1,2-hexanediol, sodiumlaurylsulfate, sodium oleate and nonionic surfactants. A sufficientlyhigh effect can be obtained by adding from 10 to 30 mass % of thepenetration accelerator in the ink. The penetration accelerator ispreferably used in an amount of causing no blurring of printed letter orno print through.

Examples of the ultraviolet absorbent which can be used in the presentinvention for improving the preservability of image includebenzotriazole-base compounds described in JP-A-58-185677,JP-A-61-190537, JP-A-2-782, JP-A-5-197075 and JP-A-9-34057,benzophenone-base compounds described in JP-A-46-2784, JP-A-5-194483 andU.S. Pat. No. 3,214,463, cinnamic acid-base compounds described inJP-B-48-30492 (the term “JP-B” as used herein means an “examinedJapanese patent publication”), JP-B-56-21141 and JP-A-10-88106,triazine-base compounds described in JP-A-4-298503, JP-A-8-53427,JP-A-8-239368, JP-A-10-182621 and JP-T-8-501291 (the term “JP-T” as usedherein means a “published Japanese translation of a PCT patentapplication”), compounds described in Research Disclosure No. 24239, andcompounds of absorbing ultraviolet light and emitting fluorescent light,so-called fluorescent brightening agents, as represented bystilbene-base compounds and benzoxazole-base compounds.

As for the antioxidant which is used in the present invention forimproving the preservability of image, various organic or metalcomplex-base discoloration inhibitors can be used. Examples of theorganic discoloration inhibitor include hydroquinones, alkoxyphenols,dialkoxyphenols, phenols, anilines, amines, indanes, chromans,alkoxyanilines and heterocyclic rings. Examples of the metal complexinclude nickel complex and zinc complex. More specifically, compoundsdescribed in patents cited in Research Disclosure, Nos. 17643 (ItemsVII-I to VII-J), 15162, 18716 (page 650, left column), 36544 (page 527),307105 (page 872) and 15162, and compounds included in formulae ofrepresentative compounds and in exemplary compounds described inJP-A-62-215272 (pages 127 to 137) can be used.

Examples of the fungicide for use in the present invention includesodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide,ethyl p-hydroxybenzoate, 1,2-benzisothiazolin-3-one and salts thereof.In the ink, the fungicide is preferably used in an amount of 0.02 to5.00 mass %.

The fungicide is described in detail, for example, in Bokin Bobai ZaiJiten (Dictionary of Microbicide and Fungicide), compiled by NipponBokin Bobai Gakkai Jiten Henshu Iinkai.

Examples of the rust inhibitor include acidic sulfite, sodiumthiosulfate, ammonium thioglycolate, diisopropyl-ammonium nitrite,pentaerythritol tetranitrate, dicyclohexylammonium nitrite andbenzotriazole. In the ink, the rust inhibitor is preferably used in anamount of 0.02 to 5.00 mass %.

In the ink of the present invention, a pH adjusting agent may be used.The pH of the ink solution is preferably from 4 to 12, more preferablyfrom 5 to 10, still more preferably from 6 to 9.

Examples of the pH adjusting agent include organic bases and inorganicalkalis for giving a basic pH, and organic acids and inorganic acids forgiving an acidic pH.

Examples of the organic base include triethanolamine, diethanolamine,N-methyldiethanolamine and dimethylethanol-amine. Examples of theinorganic alkali include alkali metal hydroxides (e.g., sodiumhydroxide, lithium hydroxide, potassium hydroxide), alkali metalcarbonates (e.g., sodium carbonate, sodium hydrogencarbonate) andammonium. Examples of the organic acid include an acetic acid, apropionic acid, a trifluoroacetic acid and an alkylsulfonic acid.Examples of the inorganic acid include a hydrochloric acid, a sulfuricacid and a phosphoric acid.

In the present invention, apart from the above-described surfactants, anonionic, cationic or anionic surfactant is used as the surface tensionadjusting agent. Examples thereof include anionic surfactants such asfatty acid salt, alkylsulfuric ester salt, alkylbenzenesulfonate,alkylnaphthalenesulfonate, dialkylsulfosuccinate, alkylphosphoric estersalt, naphthalenesulfonic acid formalin condensate andpolyoxyethylenealkylsulfuric ester salt, and nonionic surfactants suchas polyoxyethylene alkyl ether, polyoxyethylene alkylallyl ether,polyoxyethylene fatty acid ester, sorbitan fatty acid ester,polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylamine,glycerin fatty acid ester and oxyethylene oxypropylene block copolymer.Also, SURFYNOLS (produced by Air Products & Chemicals), which are anacetylene-base polyoxyethylene oxide surfactant, are preferably used.Furthermore, amine oxide-type amphoteric surfactants such asN,N-dimethyl-N-alkylamine oxide are preferred. In addition, surfactantsdescribed in JP-A-59-157636 (pages (37) to (38)) and ResearchDisclosure, No. 308119 (1989) can also be used.

The surface tension of the ink of the present invention is preferablyfrom 20 to 60 mN/m, more preferably from 25 to 45 mN/m.

The ink of the present invention preferably has a viscosity of 30 mPa.sor less. The viscosity is more preferably adjusted to 20 mPa.s or less.For the purpose of adjusting the viscosity, a viscosity adjusting agentis sometimes used. Examples of the viscosity adjusting agent includewater-soluble polymers such as celluloses and polyvinyl alcohol, andnonionic surfactants. The viscosity adjusting agent is described indetail in Nendo Chosei Gijutsu (Viscosity Adjusting Technology), Chap.9, Gijutsu Joho Kyokai (1999), and Inkjet Printer Yo Chemicals (98Zoho)—Zairyo no Kaihatsu Doko·Tenbo Chosa—(Chemicals for Inkjet Printer(Enlarged Edition of 98)—Survey on Development Tendency·Prospect ofMaterials—), pp. 162-174, CMC (1997).

In the present invention, if desired, various cationic, anionic ornonionic surfactants described above may be used as a dispersant or adispersion stabilizer, and fluorine- or silicone-base compounds orchelating agents as represented by EDTA may be used as a defoamingagent.

The ink set of the present invention is described below. The ink set ofthe present invention comprises two or more color inks. In particular,for realizing a full color, an ink set containing at least three primarycolor inks by the subtractive color process is preferred. For improvingthe letter or image quality, the ink set preferably further contains ablack color ink.

In these ink sets, for enhancing the gradation reproducibility andgraininess of the color image, two or more light and deep color inks arepreferably used in combination. As for the yellow color, a dark yellowink having mixed therein a slight amount of cyan or black dye can alsobe preferably used.

The ink set is preferably used in a portable form by using a cartridge.The ink cartridge may be used as a set of black ink and color ink or asan ink set of all independent colors.

The recording material (preferably recording paper or recording film)for use in the present invention is described below. The support whichcan be used for the recording paper or film is produced, for example,from a chemical pulp such as LBKP and NBKP, a mechanical pulp such asGP, PGW, RMP, TMP, CTMP, CMP and CGP, or a waste paper pulp such as DIP,by mixing, if desired, conventionally known additives such as pigment,binder, sizing agent, fixing agent, cation agent and paper strengthincreasing agent, and then sheeting the mixture by using various devicessuch as Fourdrinier paper machine and cylinder paper machine. Other thanthese supports, synthetic paper or plastic film sheet may be used as thesupport. The thickness of the support is preferably from 10 to 250 μmand the basis weight is preferably from 10 to 250 g/m².

An image-receiving layer and a backcoat layer may be provided on thesupport as it is to produce an image-receiving material for the ink ofthe present invention, or after providing a size press or an anchor coatlayer by using starch, polyvinyl alcohol or the like, an image-receivinglayer and a backcoat layer may be provided to produce an image-receivingmaterial. The support may be further subjected to a flattening treatmentby a calendering device such as machine calender, TG calender and softcalender.

In the present invention, the support is preferably paper or plasticfilm of which both surfaces are laminated with polyolefin (for example,polyethylene, polystyrene, polybutene or a copolymer thereof) orpolyethylene terephthalate. In the polyolefin, a white pigment (forexample, titanium oxide or zinc oxide) or a tinting dye (for example,cobalt blue, ultramarine or neodymium oxide) is preferably added.

The image-receiving layer provided on the support contains a porousmaterial and an aqueous binder. Also, the image-receiving layerpreferably contains a pigment and the pigment is preferably a whitepigment. Examples of the white pigment include inorganic white pigmentssuch as calcium carbonate, kaolin, talc, clay, diatomaceous earth,synthetic amorphous silica, aluminum silicate, magnesium silicate,calcium silicate, aluminum hydroxide, alumina, lithopone, zeolite,barium sulfate, calcium sulfate, titanium dioxide, zinc sulfide and zinccarbonate, and organic pigments such as styrene-base pigment, acryl-basepigment, urea resin and melamine resin. Among these, porous inorganicwhite pigments are preferred, and synthetic amorphous silica and thelike having a large pore area are more preferred. The syntheticamorphous silica may be either a silicic acid anhydride obtained by adry production process (gas phase process) or a silicic acid hydrateobtained by a wet production process, but a silicic acid hydrate ispreferred. Two or more of these pigments may be used in combination.

Examples of the aqueous binder contained in the image-receiving layerinclude water-soluble polymers such as polyvinyl alcohol,silanol-modified polyvinyl alcohol, starch, cationized starch, casein,gelatin, carboxymethyl cellulose, hydroxyethyl cellulose,polyvinylpyrrolidone, polyalkylene oxide and polyalkylene oxidederivative, and water-dispersible polymers such as styrene butadienelatex and acryl emulsion. These aqueous binders can be used individuallyor in combination of two or more thereof. Among these, polyvinyl alcoholand silanol-modified polyvinyl alcohol are preferred in the presentinvention in view of adhesion to the pigment and peeling resistance ofthe image-receiving layer.

The image-receiving layer may contain a mordant, a water-proofing agent,a light fastness enhancer, a gas resistance enhancer, a surfactant, ahardening agent and other additives in addition to the pigment andaqueous binder.

The mordant added to the image-receiving layer is preferably immobilizedand for this purpose, a polymer mordant is preferably used.

The polymer mordant is described in JP-A-48-28325, JP-A-54-74430,JP-A-54-124726, JP-A-55-22766, JP-A-55-142339, JP-A-60-23850,JP-A-60-23851, JP-A-60-23852, JP-A-60-23853, JP-A-60-57836,JP-A-60-60643, JP-A-60-118834, JP-A-60-122940, JP-A-60-122941,JP-A-60-122942, JP-A-60-235134, JP-A-1-161236 and U.S. Pat. Nos.2,484,430, 2,548,564, 3,148,061, 3,309,690, 4,115,124, 4,124,386,4,193,800, 4,273,853, 4,282,305 and 4,450,224. An image-receivingmaterial containing the polymer mordant described in JP-A-1-161236(pages 212 to 215) is particularly preferred. When the polymer mordantdescribed in this patent publication is used, an image having excellentimage quality can be obtained and at the same time, the light fastnessof the image is improved.

The water-proofing agent is effective for obtaining a water-resistantimage. The water-proofing agent is preferably a cationic resin. Examplesof the cationic resin include polyamidopolyamine epichlorohydrin,polyethyleneimine, polyaminesulfone, poly-dimethyldiallyl-ammoniumchloride and cation polyacrylamide. The content of the cationic resin ispreferably from 1 to 15 mass %, more preferably from 3 to 10 mass %,based on the entire solid content of the ink-receiving layer.

Examples of the light fastness enhancer and the gas resistance enhancerinclude phenol compounds, hindered phenol compounds, thioethercompounds, thiourea compounds, thiocyanic acid compounds, aminecompounds, hindered amine compounds, TEMPO compounds, hydrazinecompounds, hydrazide compounds, amidine compounds, vinylgroup-containing compounds, ester compounds, amide compounds, ethercompounds, alcohol compounds, sulfinic acid compounds, saccharides,water-soluble reducing compounds, organic acids, inorganic acids,hydroxy group-containing organic acids, benzotriazole compounds,benzophenone compounds, triazine compounds, heterocyclic compounds,water-soluble metal salts, organic metal compounds and metal complexes.

Specific examples of these compounds include those described inJP-A-10-182621, JP-A-2001-260519, JP-A-2000-260519, JP-B-4-34953,JP-B-4-34513, JP-B-4-34512, JP-A-11-170686, JP-A-60-67190,JP-A-7-276808, JP-A-2000-94829, JP-T-8-512258 and JP-A-11-321090.

Examples of the light fastness enhancer include zinc sulfate, zincoxide, hindered amine-base antioxidants, and benzotriazole-baseultraviolet absorbents such as benzophenone. Among these, zinc sulfateis preferred.

The surfactant functions as a coating aid, a releasability improver, aslipperiness improver or an antistatic agent. This surfactant isdescribed in JP-A-62-173463 and JP-A-62-183457.

Instead of the surfactant, an organofluoro compound may be used. Theorganofluoro compound is preferably hydrophobic. Examples of theorganofluoro compound include fluorine-containing surfactants, oilyfluorine-base compounds (for example, fluorine oil) and solid fluorinecompound resins (for example, ethylene tetrafluoride resin) Theorganofluoro compound is described in JP-B-57-9053 (columns 8 to 17),JP-A-61-20994 and JP-A-62-135826.

As the hardening agent, for example, the materials described inJP-A-1-161236 (page 222), JP-A-9-263036, JP-A-10-119423 andJP-A-2001-310547 can be used.

Other examples of the additive added to the image-receiving layerinclude a pigment dispersant, a thickener, a defoaming agent, a dye, afluorescent brightening agent, an antiseptic, a matting agent and ahardening agent. The image-receiving layer may be composed of one layeror two layers.

In the recording paper or film, a backcoat layer may also be provided.Examples of the component which can be added to this layer include awhite pigment, an aqueous binder and other components.

Examples of the white pigment contained in the backcoat layer includeinorganic white pigments such as precipitated calcium carbonate, heavycalcium carbonate, kaolin, talc, calcium sulfate, barium sulfate,titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white,aluminum silicate, diatomaceous earth, calcium silicate, magnesiumsilicate, synthetic amorphous silica, colloidal silica, colloidalalumina, pseudo-boehmite, aluminum hydroxide, alumina, lithopone,zeolite, hydrolyzed halloysite, magnesium carbonate and magnesiumhydroxide, and organic pigments such as styrene-base plastic pigment,acryl-base plastic pigment, polyethylene, microcapsule, urea resin andmelamine resin.

Examples of the aqueous binder contained in the backcoat layer includewater-soluble polymers such as styrene/maleate copolymer,styrene/acrylate copolymer, polyvinyl alcohol, silanol-modifiedpolyvinyl alcohol, starch, cationized starch, casein, gelatin,carboxymethyl cellulose, hydroxyethyl cellulose andpolyvinylpyrrolidone, and water-dispersible polymers such as styrenebutadiene latex and acryl emulsion. Other examples of the componentcontained in the backcoat layer include a defoaming agent, a foaminhibitor, a dye, a fluorescent brightening agent, an antiseptic and awater-proofing agent.

In a constituent layer (including the back layer) of the inkjetrecording paper or film, a polymer fine particle dispersion may beadded. The polymer fine particle dispersion is used for the purpose ofimproving film properties, for example, stabilizing the dimension andpreventing the curling, adhesion or film cracking. The polymer fineparticle dispersion is described in JP-A-62-245258, JP-A-62-1316648 andJP-A-62-110066. When a polymer fine particle dispersion having a lowglass transition temperature (40° C. or less) is added to a layercontaining a mordant, the layer can be prevented from cracking orcurling. The curling can be prevented also by adding a polymer fineparticle dispersion having a high glass transition temperature to theback layer.

The ink of the present invention is not limited in the inkjet recordingsystem to which the ink is applied, and is used for a known system, forexample, an electric charge control system of jetting out the ink byutilizing the electrostatic induction force, a drop-on-demand system(pressure pulse system) utilizing an oscillation pressure of apiezoelectric element, an acoustic inkjet system of converting electricsignals into acoustic beams, irradiating the beams on the ink andjetting out the ink by utilizing the radiation pressure, and a thermalinkjet (bubble jet) system of heating the ink to form a bubble andutilizing the pressure generated.

The inkjet recording system includes a system of ejecting a large numberof small-volume ink droplets of a so-called photo ink having a lowconcentration, a system of improving the image quality by using aplurality of inks having substantially the same color hue but differingin the concentration, and a system using a colorless transparent ink.

The inkjet recording ink of the present invention can also be used foruses other than the inkjet recording, such as a material for displayimage, an image-forming material for interior decoration, and animage-forming material for outdoor decoration.

The material for display image indicates various materials such asposter, wallpaper, ornamental goods (e.g., ornament, doll), handbill forcommercial advertisement, wrapping paper, wrapping material, paper bag,vinyl bag, package material, billboard, image drawn on or attached tothe side face of traffic (e.g., automobile, bus, electric car), andclothing with a logo. In the case of using the dye of the presentinvention as a material for forming a display image, the image includesnot only a strict image but also all patterns by a dye, which can beperceived by a human, such as abstract design, letter and geometricalpattern.

The material for interior decoration indicates various materials such aswallpaper, ornamental goods (e.g., ornament, doll), luminaire member,furniture member and design member of floor or ceiling. In the case ofusing the dye of the present invention as a material for forming animage, the image includes not only a strict image but also all patternsby a dye, which can be perceived by a human, such as abstract design,letter and geometrical pattern.

The material for outdoor decoration indicates various materials such aswall material, roofing material, billboard, gardening material, outdoorornamental goods (e.g., ornament, doll) and outdoor luminaire member. Inthe case of using the dye of the present invention as a material forforming an image, the image includes not only a strict image but alsoall patterns by a dye, which can be perceived by a human, such asabstract design, letter and geometrical pattern.

In these uses, examples of the medium on which the pattern is formedinclude various materials such as paper, fiber, cloth (includingnon-woven fabric), plastic, metal and ceramic. Examples of the dyeingform include mordanting, printing and fixing of a coloring matter in theform of a reactive dye having introduced thereinto a reactive group.Among these, preferred is dyeing by mordanting.

EXAMPLES

The present invention is described below by referring to Examples, butthe present invention is not limited thereto.

Example 1

Deionized water was added to the following components to make 1 literand the resulting solution was stirred for 1 hour under heating at 30 to40° C. and then filtered under reduced pressure through a microfilterhaving an average pore size of 0.25 μm to prepare Light Magenta InkSolution LM-101. [Formulation of Light Magenta Ink LM-101] (SolidContents) Magenta Dye (a-36) of the present  7.5 g/liter inventionProxel  3.5 g/liter (Liquid Components) Diethylene glycol (DEG)  150g/liter Glycerin (GR)  130 g/liter Triethylene glycol monobutyl ether(TGB)  130 g/liter Triethanolamine (TEA)  6.9 g/liter Surfynol STG (SW:nonionic surfactant)   10 g/liter

Also, Magenta Ink Solution M-101 was prepared by increasing Magenta Dye(a-36) to 23 g in the formulation above. [Formulation of Magenta InkM-101] (Solid Contents) Magenta Dye (a-36) of the present   23 g/literinvention Proxel  3.5 g/liter (Liquid Components) Diethylene glycol  150g/liter Glycerin  130 g/liter Triethylene glycol monobutyl ether  130g/liter Triethanolamine  6.9 g/liter Surfynol STG   10 g/liter

Inks LM-102 to LM-108 and Inks M-102 to M-108 each having thoroughly thesame composition as LM-101 or M-101 except for adding an additive asshown in Table below were produced. Additive LM-101, M-101 none(Comparative Example) LM-102, M-102 10 g/liter of POEP-1 to LM-101,M-101 (Comparative Example) LM-103, M-103 10 g/liter of POEN-1 toLM-101, M-101 (Comparative Example) LM-104, M-104 (Invention) 10 g/literof W-1 to LM-101, M-101 LM-105, M-105 (Invention) 10 g/liter of W-5 toLM-101, M-101 LM-106, M-106 (Invention) 10 g/liter of W-9 to LM-101,M-101 LM-107, M-107 (Invention) 10 g/liter of W-12 to LM-101, M-101LM-108, M-108 (Invention) 10 g/liter of W-16 to LM-101, M-101In Table,

-   POEP-1: Polyoxyethylene nonylphenyl ether (PEO chain: 30 on average)-   POEN-1: Polyoxyethylene naphthyl ether (PEO chain: 50 on average)

These inks each was filled in a magenta ink·light magenta ink cartridgeof an inkjet printer PM-950C (manufactured by Seiko Epson Corporation)and by using the inks of PM-950C for other colors, a magentamonochromatic image was printed. The image-receiving sheet where theimage was printed was inkjet paper Photo Gloss Paper EX produced by FujiPhoto Film Co., Ltd. The image obtained was evaluated on the ejectionproperty of ink and the fastness of image.

(Evaluation Test)

1) As for the ejection stability, cartridges were set in the printer andafter confirming the ejection of ink from all nozzles, the image wasoutput on 20 sheets of A4-size paper and rated based on the followingcriteria:

-   -   A: Printing was not disordered from start to end of printing.    -   B: Printing was disordered in some outputs.    -   C: Printing was disordered from start to end of printing.

2) As for the image preservability, a magenta solid image printed samplewas prepared and subjected to the following evaluations.

(1) In the evaluation of light fastness, the image density Ciimmediately after printing was measured by X-Rite 310 and after theimage was irradiated with xenon light (85,000 lx) for 10 days by using aweather meter manufactured by Atlas, the image density Cf was againmeasured. Then, the dye residual ratio Cf/Ci×100 was determined andevaluated. The dye residual ratio was evaluated at three points having areflection density of 1, 1.5 and 2. The sample was rated A when the dyeresidual ratio was 70% or more at any density, rated B when less than70% at two points, and rated C when less than 70% at all points.

(2) In the evaluation of heat fastness, the density was measured byX-Rite 310 before and after the sample was stored for 10 days under theconditions of 80° C. and 15% RH, and the dye residual ratio wasdetermined and evaluated. The dye residual ratio was evaluated at threepoints having a reflection density of 1, 1.5 and 2. The sample was ratedA when the dye residual ratio was 90% or more at any density, rated Bwhen less than 90% at two points, and rated C when less than 90% at allpoints.

(3) In the evaluation of ozone resistance, the photo gloss paper havingformed thereon the image was left standing for 7 days in a box set to anozone gas concentration of 0.5 ppm and the image density before andafter standing in the ozone gas atmosphere was measured by a reflectiondensitometer (X-Rite 310TR) and evaluated in terms of the coloringmatter residual ratio. The reflection density was measured at threepoints of 1, 1.5 and 2.0. The ozone gas concentration in the box was setby using an ozone gas monitor (Model OZG-EM-01) manufactured by APPLICS.

The sample was rated on a three-stage scale, namely, rated A when thecoloring matter residual ratio was 80% or more at any density, rated Bwhen less than 80% at one or two point(s), and rated C when less than70% at all points.

3) As for the blurring of the image under high-humidity condition, aprinting pattern where four magenta square patterns each in a size of 3cm×3 cm were arrayed to form a two-line and two-column table shape witha 1-mm white clearance between respective square patterns was preparedand after this image sample was stored for 72 hours under the conditionsof 25° C. and 90% RH, the bleeding of magenta dye in the white clearancewas observed. The sample was rated A when the increase of magentadensity in the white clearance based on the density immediately afterprinting was less than 0.01 as measured by a magenta filter of Status A,rated B when from 0.01 to 0.05, and rated C when more than 0.05.

The results obtained are shown in Table below. Ejection Light Heat O₃ MProperty Fastness Fastness Resistance Bleeding Genuine ink of A C B C BEPSON (PM-950C) LM-101, A A A A C M-101 (Comparative Example) LM-102, AA A A C M-102 (Comparative Example) LM-103, A A A A C M-103 (ComparativeExample) LM-104, A A A A A M-104 (Invention) LM-105, A A A A A M-105(Invention) LM-106, A A A A A M-106 (Invention) LM-107, A A A A A M-107(Invention) LM-108, A A A A A M-108 (Invention)

As seen from the results in the Table, the systems using the inkcomposition of the present invention surpassed Comparative Examples inview of magenta bleeding (M bleeding) and surpassed the ink of EPSON(genuine ink of PM-950C) in view of fastness of the coloring matter.

Example 2 Preparation of Light Cyan Ink LC-101 (Comparative Example)

Deionized water was added to the following components to make 1 literand the resulting solution was stirred for 1 hour under heating at 30 to40° C. and then filtered under reduced pressure through a microfilterhaving an average pore size of 0.25 μm to prepare Light Cyan InkSolution (LC-101). [Formulation of Light Cyan Ink LC-101] (SolidContents) Cyan coloring matter of the present 17.5 g/liter invention(Compound 154) Proxel  3.5 g/liter (Liquid Components) Diethylene glycol 150 g/liter Glycerin  130 g/liter Triethylene glycol monobutyl ether 130 g/liter Triethanolamine  6.9 g/liter Surfynol STG (SW: nonionicsurfactant)   10 g/liter

Also, Cyan Ink Solution C-101 was prepared by increasing the cyancoloring matter (154) to 68 g in the formulation above. [Formulation ofCyan Ink C-101] (Solid Contents) Cyan coloring matter of the present  68 g/liter invention (Compound 154) Proxel  3.5 g/liter (LiquidComponents) Diethylene glycol  150 g/liter Glycerin  130 g/literTriethylene glycol monobutyl ether  130 g/liter Triethanolamine  6.9g/liter Surfynol STG   10 g/liter

Inks LC-102 to LC-108 and Inks C-102 to C-108 each having thoroughly thesame composition as LC-101 or C-101 except for adding an additive asshown in Table below were produced. Additive LC-101, C-101 none(Comparative Example) LC-102, C-102 10 g/liter of POEP-1 to LC-101,C-101 (Comparative Example) LC-103, C-103 10 g/liter of POEN-1 toLC-101, C-101 (Comparative Example) LC-104, C-104 (Invention) 10 g/literof W-1 to LC-101, C-101 LC-105, C-105 (Invention) 10 g/liter of W-5 toLC-101, C-101 LC-106, C-106 (Invention) 10 g/liter of W-9 to LC-101,C-101 LC-107, C-107 (Invention) 10 g/liter of W-12 to LC-101, C-101LC-108, C-108 (Invention) 10 g/liter of W-16 to LC-101, C-101POEP-1: Polyoxyethylene nonylphenyl ether (PEO chain: 30 on average)POEN-1: Polyoxyethylene naphthyl ether (PEO chain: 50 on average)

The inks prepared above each was filled in a cyan ink·light cyan inkcartridge of an inkjet printer PM-950C (manufactured by Seiko EpsonCorporation) and by using the inks of PM-950C for other colors, a cyanmonochromatic image was printed. The image-receiving sheet where theimage was printed was inkjet paper Photo Gloss Paper EX produced by FujiPhoto Film Co., Ltd. The image obtained was evaluated on the ejectionproperty of ink and the fastness of image by the following methods.

(Evaluation Test)

1) As for the ejection stability, cartridges were set in the printer andafter confirming the ejection of ink from all nozzles, the image wasoutput on 20 sheets of A4-size paper and rated based on the followingcriteria:

-   -   A: Printing was not disordered from start to end of printing.    -   B: Printing was disordered in some outputs.    -   C: Printing was disordered from start to end of printing.

2) As for the image preservability, a cyan solid image printed samplewas prepared and subjected to the following evaluations.

(1) In the evaluation of light fastness, the image density Ciimmediately after printing was measured by X-Rite 310 and after theimage was irradiated with xenon light (85,000 lx) for 10 days by using aweather meter manufactured by Atlas, the image density Cf was againmeasured. Then, the dye residual ratio (100×Cf/Ci) was determined andevaluated. The dye residual ratio was evaluated at three points having areflection density of 1, 1.5 and 2. The sample was rated A when the dyeresidual ratio was 70% or more at any density, rated B when less than70% at two points, and rated C when less than 70% at all points.

(2) In the evaluation of heat fastness, the density was measured byX-Rite 310TR before and after the sample was stored for 10 days underthe conditions of 80° C. and 15% RH and the dye residual ratio wasdetermined and evaluated. The dye residual ratio was evaluated at threepoints having a reflection density of 1, 1.5 and 2. The sample was ratedA when the dye residual ratio was 90% or more at any density, rated Bwhen less than 90% at two points, and rated C when less than 90% at allpoints.

(3) In the evaluation of ozone resistance, the photo gloss paper havingformed thereon the image was left standing for 7 days in a box set to anozone gas concentration of 0.5 ppm and the image density before andafter standing in the ozone gas atmosphere was measured by a reflectiondensitometer (X-Rite 310TR) and evaluated in terms of the coloringmatter residual ratio. The reflection density was measured at threepoints of 1, 1.5 and 2.0. The ozone gas concentration in the box was setby using an ozone gas monitor (Model OZG-EM-01) manufactured by APPLICS.

The sample was rated on a three-stage scale, namely, rated A when thecoloring matter residual ratio was 80% or more at any density, rated Bwhen less than 80% at one or two point(s), and rated C when less than70% at all points.

3) As for the blurring of the image under high-humidity condition, aprinting pattern where four cyan square patterns each in a size of 3cm×3 cm were arrayed to form a two-line and two-column table shape witha 1-mm white clearance between respective square patterns was preparedand after this image sample was stored for 72 hours under the conditionsof 25° C. and 90% RH, the bleeding of cyan dye in the white clearancewas observed. The sample was rated A when the increase of cyan densityin the white clearance based on the density immediately after printingwas less than 0.01 as measured by a cyan filter of Status A, rated Bwhen from 0.01 to 0.05, and rated C when more than 0.05.

The results obtained are shown in Table below. Ejection Light Heat O₃ CProperty Fastness Fastness Resistance Bleeding Genuine ink of A B B C BEPSON (PC-950) LC-101, A A A A C C-101 (Comparative Example) LC-102, A AA A C C-102 (Comparative Example) LC-103, A A A A C C-103 (ComparativeExample) LC-104, A A A A A C-104 (Invention) LC-105, A A A A A C-105(Invention) LC-106, A A A A A C-106 (Invention) LC-107, A A A A A C-107(Invention) LC-108, C-108 A A A A A (Invention)

As seen from the results in the Table, the systems using the inkcomposition of the present invention surpassed Comparative Examples inview of cyan bleeding (C bleeding) and surpassed the ink of EPSON(genuine ink of PM-950C) in view of fastness of the coloring matter.

Example 3

Deionized water was added to the following components to make 1 literand the resulting solution was stirred for 1 hour under heating at 30 to40° C. and then filtered under reduced pressure through a microfilterhaving an average pore size of 0.25 μm to prepare Light Magenta InkSolution LM-201. [Formulation of Light Magenta Ink LM-201] (SolidContents) Magenta coloring matter (Compound a-36  7.5 g/literexemplified as azo dye) Urea   37 g/liter (Liquid Components) Diethyleneglycol (DEG)  140 g/liter Glycerin (GR)  120 g/liter Triethylene glycolmonobutyl ether (TGB)  120 g/liter Triethanolamine (TEA)  6.9 g/literSurfynol STG (SW)   10 g/liter

Also, Magenta Ink Solution M-201 was prepared as follows by increasingthe magenta coloring matter (a-36) to 23 g in the formulation above.[Formulation of Magenta Ink M-201] (Solid Contents) Magenta coloringmatter (Compound a-36   23 g/liter exemplified as azo dye) Urea   37g/liter (Liquid Components) Diethylene glycol (DEG)  140 g/literGlycerin (GR)  120 g/liter Triethylene glycol monobutyl ether (TGB)  120g/liter Triethanolamine (TEA)  6.9 g/liter Surfynol STG   10 g/liter

Inks LM-202 to LM-208 and Inks M-202 to M-208 each having thoroughly thesame composition as LM-201 or M-201 except for adding an additive asshown in Table below were produced. Additive LM-201, M-201 none(Comparative Example) LM-202, M-202 10 g/liter of POEP-1 to LM-201,M-201 (Comparative Example) LM-203, M-203 10 g/liter of POEN-1 toLM-201, M-201 (Comparative Example) LM-204, M-204 (Invention) 10 g/literof X-1 to LM-201, M-201 LM-205, M-205 (Invention) 10 g/liter of X-5 toLM-201, M-201 LM-206, M-206 (Invention) 10 g/liter of X-9 to LM-201,M-201 LM-207, M-207 (Invention) 10 g/liter of X-12 to LM-201, M-201LM-208, M-208 (Invention) 10 g/liter of X-14 to LM-201, M-201POEP-1: Polyoxyethylene nonylphenyl ether (PEO chain: 30 on average)POEN-1: Polyoxyethylene naphthyl ether (PEO chain: 50 on average)

These inks each was filled in a magenta ink·light magenta ink cartridgeof an inkjet printer PM-950C (manufactured by Seiko Epson Corporation)and by using the inks of PM-950C for other colors, a magentamonochromatic image was printed. The image-receiving sheet where theimage was printed was inkjet paper Photo Gloss Paper EX produced by FujiPhoto Film Co., Ltd. The image obtained was evaluated on the fastness ofimage under high-humidity conditions.

(Evaluation Test)

As for the blurring (magenta bleeding) of image under high-humidityconditions, a printing pattern where four magenta square patterns eachin a size of 3 cm×3 cm were arrayed to form a two-line and two-columntable shape with a 1-mm white clearance between respective squarepatterns was prepared and after this image sample was stored for 72hours under the conditions of 25° C. and 90% RH, the bleeding of magentadye in the white clearance was observed. The sample was rated A when theincrease of magenta density in the white clearance based on the densityimmediately after printing was less than 0.01 as measured by a magentafilter of Status A, rated B when from 0.01 to 0.05, and rated C whenmore than 0.05.

The results obtained are shown in Table below. Magenta Bleeding Genuineink of EPSON (PM-950C) B LM-201, M-201 (Comparative Example) C LM-202,M-202 (Comparative Example) C LM-203, M-203 (Comparative Example) CLM-204, M-204 (Invention) A LM-205, M-205 (Invention) A LM-206, M-206(Invention) A LM-207, M-207 (Invention) A LM-208, M-208 (Invention) A

As seen from the results in the Table, the systems using the ink set ofthe present invention surpassed all Comparative Examples in view ofmagenta bleeding.

Example 4

Deionized water was added to the following components to make 1 literand the resulting solution was stirred for 1 hour under heating at 30 to40° C. and then filtered under reduced pressure through a microfilterhaving an average pore size of 0.25 μm to prepare Light Cyan InkSolution (LC-201). [Formulation of Light Cyan Ink LC-201] (SolidContents) Cyan coloring matter (Compound 154 17.5 g/liter exemplified asphthalocyanine dye) Proxel  3.5 g/liter (Liquid Components) Diethyleneglycol  150 g/liter Glycerin  130 g/liter Triethylene glycol monobutylether  130 g/liter Triethanolamine  6.9 g/liter Surfynol STG (SW:nonionic surfactant)   10 g/liter

Also, Cyan Ink Solution C-201 was prepared as follows by increasing thecyan coloring matter (Compound 154 exemplified as phthalocyanine dye) to68 g in the formulation above. [Formulation of Magenta Ink C-201] (SolidContents) Cyan coloring matter (Compound 154 68 g/liter exemplified asphthalocyanine dye) Proxel 3.5 g/liter (Liquid Components) Diethyleneglycol 150 g/liter Glycerin 130 g/liter Triethylene glycol monobutylether 130 g/liter Triethanolamine 6.9 g/liter Surfynol STG 10 g/liter

Inks LC-202 to LC-208 and Inks C-202 to C-208 each having thoroughly thesame composition as LC-201 or C-201 except for adding an additive asshown in Table below were produced. Additive LC-201, C-201 none(Comparative Example) LC-202, C-202 10 g/liter of POEP-1 to LC-201,C-201 (Comparative Example) LC-203, C-203 10 g/liter of POEN-1 toLC-201, C-201 (Comparative Example) LC-204, C-204 (Invention) 10 g/literof X-1 to LC-201, C-201 LC-205, C-205 (Invention) 10 g/liter of X-5 toLC-201, C-201 LC-206, C-206 (Invention) 10 g/liter of X-9 to LC-201,C-201 LC-207, C-207 (Invention) 10 g/liter of X-12 to LC-201, C-201LC-208, C-208 (Invention) 10 g/liter of X-14 to LC-201, C-201POEP-1: Polyoxyethylene nonylphenyl ether (PEO chain: 30 on average)POEN-1: Polyoxyethylene naphthyl ether (PEO chain: 50 on average)

These inks each was filled in a cyan ink·light cyan ink cartridge of aninkjet printer PM-950C (manufactured by Seiko Epson Corporation) and thecyan bleeding was evaluated in the same manner as in Example 3.

The results obtained are shown in Table below. Cyan Bleeding Genuine inkof EPSON (PC-950C) B LC-201, C-201 (Comparative Example) C LC-202, C-202(Comparative Example) C LC-203, C-203 (Comparative Example) C LC-204,C-204 (Invention) A LC-205, C-205 (Invention) A LC-206, C-206(Invention) A LC-207, C-207 (Invention) A LC-208, C-208 (Invention) A

As seen from the results in the Table, the systems using the ink set ofthe present invention surpassed all Comparative Examples in view of cyanbleeding.

(Effects of the Invention)

The ink composition of the present invention comprising an azo dyehaving a specific structure of formula (1) and a betaine-type surfactantis excellent in the ejection property, fastness to light and heat, andoxidation resistance and at the same time, excellent in view of magentableeding under high-humidity conditions.

INDUSTRIAL APPLICABILITY

The ink of the present invention is not limited in the inkjet recordingsystem and can be used for a known system, for example, an electriccharge control system of jetting out the ink by utilizing theelectrostatic induction force, a drop-on-demand system (pressure pulsesystem) utilizing an oscillation pressure of a piezoelectric element, anacoustic inkjet system of converting electric signals into acousticbeams, irradiating the beams on the ink and jetting out the ink byutilizing the radiation pressure, and a thermal inkjet (bubble jet)system of heating the ink to form a bubble and utilizing the pressuregenerated.

The inkjet recording system includes a system of ejecting a large numberof small-volume ink droplets of a so-called photo ink having a lowconcentration, a system of improving the image quality by using aplurality of inks having substantially the same color hue but differingin the concentration, and a system using a colorless transparent ink,and the ink of the present invention can be used for all of thesesystems.

1. An inkjet recording ink composition comprising an aqueous medium andat least one dye dissolved and/or dispersed in said aqueous medium,wherein at least one betaine-type surfactant is contained in said inkcomposition.
 2. The inkjet recording ink composition as claimed in claim1, wherein in a molecule of said betaine-type surfactant, a cationicmoiety is a quaternary nitrogen atom and an anionic moiety is a carboxylgroup or a sulfo group.
 3. The inkjet recording ink composition asclaimed in claim 1 or 2, wherein said betaine-type surfactant is acompound with a N-position of imidazole being substituted by acarboxyalkyl group (compound A), or an alkylamine salt compound havingan alkyl substituted by a carboxyl group or a sulfo group (compound B).4. The inkjet recording ink composition as claimed in claim 3, whereinsaid compound A is a compound represented by formula (A):

wherein R_(s1) and R_(s2) each represents an alkyl group, and R_(s3)represents a carboxyl or sulfo group-containing alkyl group.
 5. Theinkjet recording ink composition as claimed in claim 3, wherein saidcompound B is a compound represented by formula (B):

wherein R_(s4), R_(s5) and R_(s6) each independently represents an alkylgroup, an aryl group or a heterocyclic group and may combine with eachother to form a ring structure, and R_(s7) represents a carboxyl orsulfo group-containing alkyl group.
 6. The inkjet recording inkcomposition as claimed in claim 5, wherein in said compound representedby formula (B), R_(s4), R_(s5) and R_(s6) each independently representsan alkyl group and a group represented by R_(s7) is represented by-L-COO⁻, in which L represents a linking group.
 7. The inkjet recordingink composition as claimed in claim 6, wherein in said compoundrepresented by formula (B), L represents CH(R_(s8)), R_(s8) represents ahydrogen atom or an alkyl group having 8 or more carbon atoms, and atleast one of R_(s4), R_(s5), R_(s6) and R_(s8) is an alkyl group having8 or more carbon atoms.
 8. The inkjet recording ink composition asclaimed in any one of claims 1 to 7, wherein said dye is an azo dyehaving an absorption maximum in a spectral region of 500 to 580 nm insaid aqueous medium and having an oxidation potential nobler than 1.0 V(vs SCE).
 9. The inkjet recording ink composition as claimed in any oneof claims 1 to 8, wherein said azo dye has a chromophore represented bythe formula: (heterocyclic ring A) —N═N— (heterocyclic ring B), providedthat the heterocyclic ring A and the heterocyclic B may have samestructure.
 10. The inkjet recording ink composition as claimed in anyone of claims 1 to 9, wherein said azo dye is an azo dye in which anaromatic nitrogen-containing 6-membered heterocyclic ring is bonded as acoupling component directly to at least one side of an azo group. 11.The inkjet recording ink composition as claimed in any one of claims 1to 10, wherein said azo dye is an azo dye having an aromatic ring aminogroup- or heterocyclic amino group-containing structure as anauxochrome.
 12. The inkjet recording ink as claimed in any one of claims1 to 11, wherein said azo dye is an azo dye having a steric structure.13. The inkjet recording ink composition as claimed in any one of claims1 to 12, wherein said azo dye is a dye represented by the followingformula (1):

wherein A represents a 5-membered heterocyclic group; B¹ and B² eachrepresents ═CR¹— or —CR²═ or either one of B¹ and B² represents anitrogen atom and other represents ═CR¹— or —CR²═; R⁵ and R⁶ eachindependently represents a hydrogen atom or a substituent, saidsubstituent is an aliphatic group, an aromatic group, a heterocyclicgroup, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group,a carbamoyl group, an alkylsulfonyl group, an arylsulfonyl group or asulfamoyl group, and hydrogen atom of each substituent may besubstituted; G, R¹ and R² each independently represents a hydrogen atomor a substituent, said substituent is a halogen atom, an aliphaticgroup, an aromatic group, a heterocyclic group, a cyano group, acarboxyl group, a carbamoyl group, an alkoxycarbonyl group, anaryloxycarbonyl group, a heterocyclic oxycarbonyl group, an acyl group,a hydroxy group, an alkoxy group, an aryloxy group, a heterocyclic oxygroup, a silyloxy group, an acyloxy group, a carbamoyloxy group, analkoxycarbonyloxy group, an aryloxycarbonyloxy group, an amino group, anacylamino group, a ureido group, a sulfamoylamino group, analkoxycarbonylamino group, an aryloxycarbonylamino group, analkylsulfonylamino group, an arylsulfonylamino group, a heterocyclicsulfonylamino group, a nitro group, an alkylthio group, an arylthiogroup, a heterocyclic thio group, an alkylsulfonyl group, anarylsulfonyl group, a heterocyclic sulfonyl group, an alkylsulfinylgroup, an arylsulfinyl group, a heterocyclic sulfinyl group, a sulfamoylgroup or a sulfo group, and hydrogen atom of each substituent may besubstituted; and R¹ and R⁵, or R⁵ and R⁶ may combine to form a 5- or6-membered ring.
 14. The inkjet recording ink composition as claimed inany one of claims 1 to 13, wherein an ozone discoloration rate constantof recorded image is 5.0×10⁻² [hour⁻¹] or less.
 15. The inkjet recordingink composition as claimed in any one of claims 1 to 7, wherein said dyeis a water-soluble phthalocyanine dye having an oxidation potentialnobler than 1.0 V.
 16. The inkjet recording ink composition as claimedin any one of claims 1 to 7 and 15, wherein after storage in an ozoneenvironment of 5 ppm for 24 hours, a monochromatic moiety printed byusing a single (cyan) color of said ink to give a cyan reflectiondensity of 0.9 to 1.1 in a Status A filter has a coloring matterresidual ratio (density after discoloration/initial density×100) of 60%(preferably 80%) or more.
 17. The inkjet recording ink composition asclaimed in any one of claims 1 to 7, 15 and 16, wherein afterdiscoloration with ozone under conditions of claim 16, an amount of Cuion flowed out from said ink into water is 20% or less of all dyes. 18.The inkjet recording ink composition as claimed in any one of claims 1to 7 and 15 to 17, wherein said phthalocyanine dye is a water-solubledye having an electron-withdrawing group at a β-position of a benzenering of said phthalocyanine.
 19. The inkjet recording ink composition asclaimed in any one of claims 1 to 7 and 15 to 18, wherein saidphthalocyanine dye is a water-soluble phthalocyanine dye produced by aprocess not passing through sulfonation of an unsubstitutedphthalocyanine.
 20. The inkjet recording ink composition as claimed inclaims 1 to 7 and 15 to 19, wherein said phthalocyanine dye isrepresented by the following formula (I):

wherein X₁, X₂, X₃ and X₄ each independently represents —SO-Z, —SO₂-Z,—SO₂NR1R2, a sulfo group, —CONR1R2 or —CO₂R1; Z represents a substitutedor unsubstituted alkyl group, a substituted or unsubstituted cycloalkylgroup, a substituted or unsubstituted alkenyl group, a substituted orunsubstituted aralkyl group, a substituted or unsubstituted aryl group,or a substituted or unsubstituted heterocyclic group, and R1 and R2 eachindependently represents a hydrogen atom, a substituted or unsubstitutedalkyl group, a substituted or unsubstituted cycloalkyl group, asubstituted or unsubstituted alkenyl group, a substituted orunsubstituted aralkyl group, a substituted or unsubstituted aryl group,or a substituted or unsubstituted heterocyclic group, provided that whena plurality of Zs are present, these may be same or different; Y₁, Y₂,Y₃ and Y₄ each independently represents a monovalent substituent;provided that when a plurality of X₁s, X₂s, X₃s, X₄s, Y₁s, Y₂s, Y₃s orY₄s are present, these may be same or different; a₁ to a₄ and b₁ to b₄represent a number of substituents X₁ to X₄ and Y₁ to Y₄, respectively,a₁ to a₄ each independently represents an integer of 0 to 4 but all arenot 0 at a same time, and b₁ to b₄ each independently represents aninteger of 0 to 4; and M represents a hydrogen atom, a metal atom or anoxide, hydroxide or halide thereof.
 21. The inkjet recording inkcomposition as claimed in claim 20, wherein said dye represented byformula (I) is a dye represented by the following formula (II):

wherein X₁₁ to X₁₄, Y₁₁ to Y₁₈ and M₁ have same meanings as X₁ to X₄, Y₁to Y₄ and M in formula (I), respectively, and a₁₁ to a₁₄ eachindependently represents an integer of 1 or
 2. 22. The inkjet recordingink composition as claimed in any one of claims 1 to 21, wherein anonionic surfactant is contained in said ink composition.
 23. The inkjetrecording ink composition as claimed in any one of claims 1 to 22,wherein an organic solvent having a boiling point of 150° C. or more iscontained in said ink composition.
 24. An inkjet recording ink setcomprising at least one inkjet recording ink composition claimed in anyone of claims 1 to
 23. 25. An inkjet recording method comprisingrecording an image in an inkjet printer by using said inkjet recordingink composition claimed in any one of claims 1 to 23 or said ink setclaimed in claim
 24. 26. The inkjet recording method as claimed in claim25, comprising ejecting ink droplets according to recording signals onan image-receiving material including a support having thereon animage-receiving layer containing a white inorganic pigment particle,thereby recording an image on said image-receiving material, whereinsaid ink droplet comprises said inkjet recording ink composition claimedin any one of claims 1 to 23.